kanjisense

Viewing Middle Chinese through the lens of the Kan-on[show contents]

I invite you to think of the Middle Chinese notation used here as something like our imaginary friend from Heian Japan might have come up with. It doesn't reconstruct specific consonants and vowels, but it's designed to bring you closer to the source than any scholarly reconstruction.

This is possible in large part thanks to the on'yomi tradition. These character readings may come from Japan, but they represent the attempts of real-life speakers of Tang-era Chinese to write down the sounds of the language. This has made the on'yomi an invaluable resource for scholars and anyone else trying to understand the sounds of Middle Chinese. Therefore, this notation uses the on'yomi as a starting point—in particular, those on'yomi which were recorded by Japanese speakers around the Tang dynasty, known as Kan-on.

The foundation of this notation consists of a rendition of the Kan-on using ordinary Latin letters taken from the standard conventions of romanized Japanese. Additional symbols are introduced in order to represent other distinctions which were not recorded in the Kan-on tradition, without committing to precise phonetic values. To illustrate, let's take an example of a few characters which are read with the on'yomi カ ka. In our notation, each of them is written like ⟨ka⟩, but with slight variations.

• 歌 ka
• 家 kạ
• 佳 kạ̈

The different diacritic marks on A are a sign that these vowels were somehow different from each other, though the exact nature of these differences is not universally agreed upon. The specific usage of these diacritics is meant to tell us a few things.

• Both ⟨kạ⟩ and ⟨kạ̈⟩ share the underdot mark as a way of signalling that scholars put them together in a group separate from bare ⟨ka⟩. This group is generally reconstructed with more front vowels, like [a] [æ] [ɛ] (closer to the A in cat or the E in bed), as opposed to the more back vowel in ⟨ka⟩ [ɑ] (closer to the A in father). In addition, scholars sometimes reconstruct these syllables with a velar or palatal element before the vowel like [ɣ] or [j].
• Between ⟨kạ⟩ and ⟨kạ̈⟩, the double-dot is a way of signalling another difference—namely, it's likely that the ⟨kạ̈⟩ had a higher or more front vowel. So scholars posit for 家 ⟨kạ⟩ sounds like /kɣæ/, /kjaː/, etc., whereas 佳 ⟨kạ̈⟩ gets something like /kɣɛ/, /kjaːj/ etc.

Hopefully now you can see why it's not so easy to represent Middle Chinese vowels in the International Phonetic Alphabet. The IPA only allows us to represent one scholar's reconstruction at a time. It allows us to do so with great precision, but such precision isn't always desirable. The inherent imprecision of a notation like ours actually has its advantages. By avoiding precise phonetic symbols, we avoid committing to one single scholar's vision, and we can instead express patterns that are common to many scholars' visions. This works because this notation was built on the foundation of the Kan-on tradition and other important sources which form the arsenal of all scholarly reconstructions of Middle Chinese ever published.

From Japanese to Chinese vowels [show contents]

From here on out, we will be talking about Chinese vowels with reference to the vowels of Japanese, so let's talk briefly about Japanese vowels. At the time of Kan-on, the Japanese vowel system was not very different than it is today. The so-called "Early Middle Japanese" of this period had a five-vowel system much like those of many other world languages, such as Spanish, Swahili, Hawaiian, and so on.

• /a/ Much like the A in father, as in modern Japanese.
• /i/ Much like the I in machine, as in modern Japanese.
• /u/ Much like the U in rule. This sound may have been more rounded than the corresponding sound in modern Japanese, which is often transcribed as /ɯ/.
• /e/ Narrowly transcribed [ʲe], much like the ⟨ye⟩ in yes. So the same as in modern Japanese, except with an initial glide like a Y sound.
• /o/ Narrowly transcribed [ʷo], much like the ⟨wo⟩ in worn. So the same as in modern Japanese, except with an initial glide like a W sound.

(At the beginning of the Early Middle Japanese period, there was actually an additional vowel /ə/. But this merged with the /o/ sound some time after 1000 C.E. So it still makes sense to say that the fivefold vowel system above remained intact throughout the shared history of Early Middle Japanese and Middle Chinese.)

Five-vowel systems like this just so happen to be a great match for the Latin alphabet—a coincidence which turns out to be great news for our thought experiment. Remember, we're trying to imagine how someone from Heian-era Japan might use the Latin alphabet to represent Middle Chinese sounds. And the vowels pose the biggest challenge by far because of the lack of direct evidence for Middle Chinese vowels (as opposed to the consonants, which scholars back in the day so kindly named and listed out for us).

So while we may never know exactly what the vowels of Middle Chinese sounded like, we can answer this different, also compelling question. That is, how might one best approximate the Middle Chinese vowels given just five vowel symbols? We need only to look to the on'yomi for the answer. For practically every syllable of Middle Chinese, we know exactly how Japanese speakers of the Heian period interpreted it in their own five-vowel system. These Kan-on readings will allow us to actually bring our thought experiment to a pretty satisfying conclusion, no time machine needed.

All games aside, there is a real-world lesson here for us who are trying to spell out the sounds of Middle Chinese using the Latin alphabet. There's no need to wrack our brains trying to think of the best way to write out Middle Chinese vowels in a five-vowel system. The work has already been done for us by the compilers of the Kan-on readings. These people were real contemporaries of Tang China, who knew these vowel sounds more intimately than we could ever hope to.

Caveats [show contents]

The Kan-on are a good starting point for understanding the sounds of Middle Chinese, because, in the vast majority of cases, the compilers of these on'yomi wrote down Middle Chinese sounds in a manner that was nice and consistent. But there are exceptions to this general rule. After all, the Kan-on aren't the work of one specific person like our imaginary friend from Heian Japan. They're simply a collection of character readings that happened to get recorded during this particular period of time. We can't expect them to depict the sounds of Middle Chinese in a totally systematic way.

On the other hand, the whole point of this notation is to depict Middle Chinese sounds in a systematic way. For that reason, there are some places where it deviates from Kan-on. Thankfully, these cases are few, since the Kan-on are mostly consistent. In the following section on the finals, I go into specific cases of inconsistencies within the Kan-on. But here's the general idea of how this writing system handles these inconsistencies.

Plain old inconsistencies in Kan-on

Take the character 佳. It is known to have a single Middle Chinese reading, but it has multiple Kan-on readings: /ka/ and /kai/. These are both legitimate Kan-on, since they were both recorded sometime around the Heian period. In cases like this, where there are multiple Kan-on available, this notation reflects only one of these readings in the vowel letters. So in the case of 佳, we will always write ⟨kạ̈⟩, instead of something like ⟨kạ̈i⟩. (The reasoning behind these design decisions are too complicated to go into here, but they were generally taken to keep different vowels visually distinct, and sometimes take general trends in reconstructions into account.)

Predictable vowel alternation in Kan-on

Sometimes, one Middle Chinese vowel is rendered in a couple different ways in Kan-on, but the variation happens in a pretty consistent way. For example, the characters 水 and 軌 had the same final in Chinese, but in Kan-on, they are rendered with different vowels as 水 /sui/ and 軌 /kwi/. This appears at first glance to be an inconsistency, but when we look at other words in the same category, there are clear patterns. It turns out that, for words with this final, we can usually predict the Kan-on vowel based on the initial consonant. The consonant in 軌 is a velar consonant ⟨k⟩, and whenever the initial is a velar consonant (i.e. any of ⟨kʻ⟩ ⟨kh⟩ ⟨g⟩ ⟨gh⟩), this vowel is always represented as /(w)i/ in Kan-on, as opposed to /ui/. This is just one of a few such patterns.

It's possible that these variations represent real changes in pronunciation at later stages of Middle Chinese, but that's not necessarily the case. In any event, this notation incorporates some of these patterns, above all when they are especially conspicuous and easy to explain with a general rule. This helps maintain some consistency with Kan-on, and keeps us from encroaching on the territory of reconstructions. Thus, we write those example characters' readings as 水 ⟨śuīˬ⟩ and 軌 ⟨kwīˬ⟩ You may consider the diacritics on the vowel in such cases as a hint that the vowel in question might exhibit alternation like this.

Other times, vowel alternations may be easy to explain with a general rule, but they still aren't incorporated into this notation. For example, the vowel sound in 高 is usually rendered as /au/ in Kan-on. But there's a consistent rule that, after labial consonants like /p/, the vowel is rendered /ou/, as in 宝 /pou/. Despite that, we will consistently write that vowel as ⟨au⟩, giving 髙 ⟨kau⟩ and 宝 ⟨pauˬ⟩. This lets us keep words like 宝 ⟨pauˬ⟩ and 掊 ⟨pouˬ⟩ visually distinct, without resorting to diacritics.

Many different considerations went into the decisions around which vowel alternations to honor or ignore in this writing system. Unfortunately there isn't an easy way to list them all here, so some decisions may seem kind of arbitrary. But these inconsistencies in Kan-on are rare enough that they shouldn't impact the usefulness of this notation too much—at least, this is my hope.

The structure of a final in this notation

The part of an on'yomi corresponding to the final in traditional Chinese phonology basically always consists of these elements, in this exact order:

Tones [show contents]

After the consonants and vowels in this notation, some syllables are written with a ⟨ˬ⟩ caron or a ⟨ˎ⟩ grave accent at the bottom right. These are to mark tone, an important feature of Chinese languages. This feature is reminiscent of Japanese pitch accent, but it is not the same.

If you are only interested in Middle Chinese sounds in relation to the on'yomi, you can ignore the tones to no ill effect. On the other hand, an awareness of Middle Chinese tones can be helpful for understanding the relationship between words in languages like Mandarin Chinese, Cantonese, and Vietnamese, which do have tones.

The pronunciation of the Middle Chinese tones is not known with certainty, but it is well documented that there were initially four tones recognized in ancient times. These four tones correspond only sometimes with the tones of modern Mandarin.

• Syllables with no tone mark in in this notation belong to the 平 "level" tone, the most common tone in the language. During the Tang dynasty, level-tone words may have had a high, falling pitch, or perhaps a low, steady pitch. This usually corresponds to the modern Mandarin first and second tones.
• Syllables ending with a caron ⟨ˬ⟩ in this notation belong to the 上 "rising" tone. They may have had a high pitch or a rising pitch during the Tang dynasty. This usually corresponds to modern Mandarin third tone, which is also marked with a caron (but over the vowel).
• Syllables ending with a grave accent ⟨ˎ⟩ in this notation belong to the 去 "departing" tone. They may have had a rising pitch during the Tang dynasty, like the "rising" tone, but perhaps more drawn out. This usually corresponds to modern Mandarin fourth tone, which is also marked with a grave accent (but over the vowel).
• All syllables ending with stop consonants ⟨p⟩ ⟨t⟩ ⟨k⟩ were classified as 入 "entering" tone syllables in Middle Chinese. These final consonants were lost in Mandarin, where these syllables may take on any of the four modern Mandarin tones.

The four tones eventually split on the basis of the voicing of the initial consonant. Voiced consonants had the effect of lowering the pitch of the following vowel. (In this notation, voiced consonants are any consonants NOT written with letters P, T, K, or S, or the glottal stop ⟨ʾ⟩.)

This tonal split explains the split between the first and second tones of Mandarin—the first tone is the "high level-tone", and the second tone is the "low level-tone". This high-low split also explains instances where the "rising" tone of Middle Chinese became the 4th tone of Mandarin, which is usually the result of Middle Chinese "departing" tone. The "low rising" tone and the "low departing" tone of Middle Chinese ended up merging, perhaps because the of the similar rising contours of both tones.

Finals with main vowel A [show contents]

Finals with main vowel A are divided into three different categories by scholars of Middle Chinese.

• Bare ⟨a⟩ in this notation marks finals in the category Division I. Scholars tend to reconstruct the vowel of these finals as a back vowel [ɑ], versus the more front vowels of Division II. These finals are overwhelmingly rendered as /a/ in on'yomi. The final ⟨au⟩ is sometimes interpreted as /ou/ in on'yomi, but here it is consistently represented as ⟨au⟩ to maintain a visual distinction with ⟨ou⟩.
  • The macron ⟨¯⟩ is used to distinguish ⟨āi⟩ ⟨ām⟩ ⟨āp⟩ from bare ⟨ai⟩ ⟨am⟩ ⟨ap⟩. These groups eventually merged, but at the start, the group with bare ⟨a⟩ may have had vowels that were relatively more central or shorter (variously [ʌ], [ə], [ă] in reconstructions). In some early Japanese borrowings, ⟨am⟩ ⟨ap⟩ were interpreted with the Japanese vowel -o rather than -a. While the two endings ⟨am⟩ ⟨ap⟩ were consistently permitted to rhyme with ⟨ām⟩ ⟨āp⟩ in poetry throughout the Middle Chinese period, ⟨ai⟩ and ⟨āi⟩ were not considered good rhymes until later.
  • The finals ⟨ai⟩ and ⟨wai⟩ may have been distinguished by a leading /w/-like sound before the vowel, but at least at earlier stages of Middle Chinese, some scholars attribute to ⟨wai⟩ an entirely different vowel, like /o/. If that is the case, it would explain why in some early borrowings into Japanese, ⟨wai⟩ is interpreted with -ui (rather than the expected -wai or -we).
• The underdot ⟨ ̣⟩ in this notation marks finals in the category Division II. Scholars tend to reconstruct these finals with a more front vowel than Division I, so something like [a], [æ], or even [aɨ]. It's widely agreed that these finals had an R-like or L-like sound before the vowel in Old Chinese, which may have survived into the Middle Chinese period as something like a velar glide (something like [ɰ] or [ɯ/ɣ]), or a palatal glide (like [j]). In some earlier Japanese borrowings, the vowel is interpreted as -e or -ya rather than -a. Division II finals have an affinity with retroflex consonants, which are also marked by the underdot in this notation. (The underdot was chosen for its historical association with retroflex consonants, cf. Sanskrit.)
  • The double-dot ⟨ä⟩ in this notations marks finals that were likely pronounced with a more front or higher vowel compared to finals with only the underdot, something like [ɛ] or [ai], though some scholars have posited a distinction of vowel length between these finals. (In an admittedly biased move, I chose the double-dots for their historical association with frontness, cf. German Umlaut). Finals ending in ⟨ạ̈⟩ were usually interpreted with Japanese /ai/, but sometimes with /a/; the spelling ⟨ạ̈⟩ was chosen to keep a visual distinction with ⟨ạ̈i⟩ finals, which are more consistently interpreted with /ai/. With the exception of those finals ending in ⟨ạ̈⟩, members of this group were not usually distinguished in on'yomi from their counterparts without double-dots. Both groups were often interpreted with Japanese -e in earlier borrowings. As with all the other vowels with the underdot, these likely had a preceding velar or palatal element like (something like [ɰ] [ɣ] [j]).
  • The ring ⟨°⟩ in this notation is used in finals ending in ⟨ạ̊ng⟩ and ⟨ạ̊k⟩, which scholars tend to reconstruct with an element of roundedness or height, like [ɔ] or [aɨw]. As with all the other vowels with the underdot, these may have had a preceding velar or palatal element at some earlier stages of Middle Chinese (something like [ɰ] [ɣ] [j]). In some earlier Japanese borrowings, ⟨ạ̊ng⟩ ⟨ạ̊k⟩ were interpreted with the Japanese vowel -o rather than -a. (The ring was chosen for its historical association with the letter O, cf. Danish.) These two finals are the only ones bearing the ring diacritic, reflecting the fact that they consistently formed a distinct rhyme group in Chinese poetry.
• In finals with main vowel A in this notation, the category Division III is usually marked by leading ⟨y⟩. These are usually reconstructed with an onset something like [i] or [j]. The finals ⟨yang⟩ ⟨yak⟩ are the form taken by the finals elsewhere written ⟨âng⟩ ⟨âk⟩, when a /j/ sound is present in the corresponding Kan-on reading. Finals in ⟨ya⟩ and ⟨yạ⟩ are known to have rhymed with finals in ⟨a⟩ and ⟨ạ⟩ respectively. Division III also includes the final ⟨ẃa⟩, which differs from Division I ⟨wa⟩ is that this Division III final had some kind of front element, which may have been pronounced before, after, or in combination with the element rendered /w/ in on'yomi. Scholars reconstruct this final variously as /ɨuɑ/ /ʷiɑ/ /ya/, etc.
  • The circumflex accent ⟨^⟩ is used in this notation to mark finals ⟨âng⟩ ⟨âk⟩ ⟨âi⟩ ⟨ân⟩ ⟨ât⟩ ⟨âm⟩ ⟨âp⟩. These finals may have had a Y-like sound before the vowel, and where this is reflected in on'yomi, a Y is included in this notation. Scholars tend to reconstruct these finals with a central vowel, like [ɐ]. (The circumflex accent was chosen for its historical association with central vowels, cf. Romanian, Vietnamese.) In earlier Japanese borrowings , this vowel was often interpreted with Japanese -o rather than -a. Before labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩, these vowels triggered dentilabialization.

Finals with main vowel E [show contents]

Finals with main vowel E in this notation are divided into two different categories by scholars of Middle Chinese.

• For finals written with E in this notation, the ⟨ė⟩ dot above is the usual mark of the category called Division III. Scholars tend to reconstruct the vowel of these finals with an onset something like /i/ or /j/, and a main vowel like [ɛ] or [e]. When written with the a leading ⟨y⟩ or ⟨ẁ⟩, the the dot above is omitted for the sake of brevity.
  • The circumflex accent ⟨^⟩ is used in this notation to mark finals ⟨(w)ên⟩ ⟨(w)êt⟩ ⟨(w)êm⟩ ⟨(w)êp⟩, which modern scholars generally agree had the same respective vowels as in ⟨ân⟩ ⟨ât⟩ ⟨âm⟩ ⟨âp⟩, i.e. probably a central vowel like [ɐ], which triggered dentilabialization in preceding labial consonants. In some early Japanese borrowings, these were normally interpreted with the Japanese vowel -o rather than -e.
  • The underdot ⟨ ̣⟩ is used to mark some finals in this notation ⟨ẹng⟩ ⟨ẹk⟩ which, at least at an early stage of Middle Chinese, were probably identical to the Division II finals ⟨ạng⟩ ⟨ạk⟩, except with an added /i/-like glide before the vowel, which was a front vowel along the lines of [æ].
• The bare letter E in this notation marks finals in the category Division IV. At earlier stages of Middle Chinese, these finals were probably pronounced with a vowel something like [ɛ] or [e]. That is, they were identical to the corresponding finals of Division III (with bare ⟨e⟩), but without the /i/-like glide before the vowel. Eventually, this Division IV series also was pronounced with a glide, and most (if not all) of these pairs merged.

When these finals are written the usual way, they are called "Chongniu III" finals. Some scholars believe these finals had a velar element before the vowel (the same as Division II finals). The ⟨y⟩ of "Chongniu IV" finals is a nod to borrowings from Middle Chinese into Korean, where some Chongniu IV finals were depicted with a Y-sound. These were actually not distinguished from Chongniu III finals in on'yomi.

Finals with main vowel I [show contents]

Finals with main vowel I in this notation all belong to the category known to scholars as Division III.

• The bare ⟨i⟩ is used in this notation mostly to mark finals which scholars tend to reconstruct with relatively lower or more central vowels (like [ɨ]) relative to their counterparts with the macron ⟨ī⟩ (often reconstructed with [i]). In earlier borrowings into Japanese, ⟨iu⟩ was sometimes interpreted as Japanese -eu rather than -iu, and ⟨i⟩ ⟨in⟩ ⟨it⟩ ⟨im⟩ ⟨ip⟩ were sometimes interpreted with -o rather than -i. However, finals with Y- (Chongniu IV finals) did not get interpreted with -o. All these finals were eventually to merge with their counterparts having macron ⟨ī⟩ and double-dot ⟨ï⟩. Finals in ⟨iu⟩ were sometimes interpreted as /eu/ even in the later Kan-on borrowings which form the basis of this notation, but they are consistently written ⟨iu⟩ here in order to maintain a visual distinction with ⟨eu⟩.
• The macron ⟨ī⟩ is used in this notation to mark finals which scholars sometimes reconstruct with relatively higher or more front vowels like [i] (compared to their counterparts with bare I, often reconstructed with [ɨ]). These finals were more consistently interpreted with Japanese -i (rather than -o) in earlier borrowings. The finals ⟨wī⟩ and ⟨uī⟩ were considered one and the same, but the recorders of on'yomi tended to write them differently depending on the initial consonant, so we follow suit here. The final ⟨wīk⟩ is usually written ⟨(y)ūk⟩, but after certain consonants it was depicted as /wi/ or /i/ in on'yomi, and we write it like so, though scholars consistently reconstruct these finals consistently as something along the lines of [ɨuk], [iuk] or [iwk]. Likewise, the finals ⟨wīn⟩ ⟨wīt⟩ are identified with finals ⟨yūn⟩ ⟨yūt⟩, and these were all pronounced with vowels something like [iuɪn] or [win], and in later stages may have moved towards something like [yn].
• The double-dot ⟨ï⟩ in this notation marks some vowels which scholars generally agree to have started out as an [e]-like sound in the early stages of Middle Chinese, which changed to something closer to [i]. In earlier borrowings into Japanese, ⟨ï⟩ was sometimes interpreted with Japanese -e rather than -i. (The double-dots were chosen for their historical association with the letter E, cf. German Umlaut.) This vowel eventually gained a [i]-like onset, and then the [e]-like element disappeared. The finals ⟨wï⟩ and ⟨uï⟩ were considered one and the same to the Chinese, but the recorders of Kan-on tended to write them differently depending on the initial consonant, so we follow suit here.
• The circumflex accent ⟨î⟩ in this notation marks finals which scholars tend to reconstruct as a diphthong, with a more central or back onset, something like [ɨi]. In earlier borrowings into Japanese, ⟨î⟩ was sometimes interpreted with Japanese -e rather than -i. Before labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩, this vowel triggered dentilabialization.
• The breve ⟨ĭ⟩ in this notation is used only in the final ⟨wĭk⟩ (usually reconstructed something like [wɨk], with a rounded element before a central vowel), which was considered to rhyme with ⟨yŏk⟩ (usually reconstructed something like [ɨk], the same as ⟨wĭk⟩ without the rounded element).

When these finals are written the usual way, they are called "Chongniu III" finals. Some scholars believe these finals had a velar element before the vowel (the same as Division II finals). The ⟨y⟩ of "Chongniu IV" finals is a nod to borrowings from Middle Chinese into Korean, where some Chongniu IV finals were depicted with a Y-sound. These were actually not distinguished from Chongniu III finals from in on'yomi, except in that Chongniu IV finals written with ⟨ẁ⟩ tended to lose the /w/ element, and Chongniu IV finals written with ⟨y⟩ do not alternate with o in Go-on readings.

Finals with main vowel O [show contents]

Finals with main vowel O in this notation are divided into two different categories by scholars of Middle Chinese.

• Bare ⟨o⟩ in this notation marks finals in the category Division I. Scholars tend to reconstruct the vowel of these finals as a back, rounded vowel like [o]. It's likely that the finals ⟨on⟩ ⟨ot⟩ ⟨ou⟩ were pronounced with a less rounded, more central vowel, something like [ə]. The final ⟨o⟩ with zero coda was likely rounded, and in Japanese sometimes was written as /wo/.
  • The macron ⟨ō⟩ in this notation is on finals ⟨ōng⟩ ⟨ōk⟩ to reflect a distinction between their counterparts without macron in the earlier stages of Middle Chinese. Scholars generally agree that this set with macron were pronounced with a greater degree of height, so for ⟨ōng⟩, something more like [uŋ] or [əwŋ], versus ⟨ong⟩ [oŋ] or [awŋ]. In earlier borrowings into Japanese, these finals were sometimes interpreted with Japanese -u rather than -o. These finals rhymed with finals in ⟨(i)ūng⟩ and ⟨(y)ūk⟩.
  • The breve ⟨ŏ⟩ in this notation is used to mark finals ⟨ŏng⟩ ⟨ŏk⟩ which were pronounced with a more central vowel than their counterparts without breve, something like [ə]. These finals with O-breve remained a distinct group after the merger of ⟨ōng⟩ ⟨ōk⟩ with ⟨ong⟩ ⟨ok⟩.
• In finals with main vowel O in this notation, a leading ⟨y⟩ is the usual mark of the category Division III, which scholars usually reconstruct with an initial glide (e.g. [ɨ] [i]) leading into a back or rounded vowel ( e.g. [ʌ] [ɔ]). In ⟨yo⟩, this meant a diphthong something like [ɨʌ] [iɔ] [ɨu̯o̝].
  • The breve ⟨ŏ⟩ in this notation is used to mark finals ⟨yŏng/ŷŏng⟩ ⟨yŏk/ŷŏk⟩ which rhymed with their counterparts without Y in Division I ⟨ŏng⟩ ⟨ŏk⟩. As in those finals, the element rendered as O here was probably a central, unrounded vowel, something like [ə]. At an earlier stage of Middle Chinese, these probably were more like a sequence composed of an /i/-like sound followed by /k/ or /ŋ/, and this is reflected in earlier Japanese borrowings. The final spelled ⟨ŷŏk⟩ is used in a single syllable ⟨kŷŏk⟩, which was attested in Kan-on as kyoku (not kwiyoku as suggested by the ⟨ŷ⟩), but it is spelled with ⟨ŷ⟩ to keep it visually distinct from ⟨kyŏk⟩.
  • The circumflex accent ⟨ô⟩ in this notation is used to mark finals ⟨(ŷ)ông⟩ ⟨(ŷ)ôk⟩. Especially in earlier borrowings into Japanese, these finals could be interpreted with Japanese -u rather than -io. Here we are consistently writing them with O to reflect the fact that they rhymed with finals in ⟨ong⟩ ⟨ok⟩ with bare ⟨o⟩. As in those finals, the element rendered as O here probably had a back, rounded element, something like [o] or [aw]. These finals triggered dentilabialization in preceding labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩.

Finals with main vowel U [show contents]

Finals with main vowel U in this notation all belong to the category known to scholars as Division III. After labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩, they trigger dentilabialization.

• The finals written ⟨u⟩ and ⟨yu⟩ in this notation are usually reconstructed by scholars with a back, rounded vowel like [u]. These two finals were considered one and the same in Middle Chinese, but they are written differently here depending on the initial consonant to reflect their rendering in Kan-on. After ⟨t⟩ ⟨tʻ⟩ ⟨d⟩ ⟨n⟩, this final is rendered consistently as /iu/ in Kan-on, but it is written here as ⟨yu⟩ to maintain a visual distinction with ⟨iu⟩. This final is rendered more inconsistently in Kan-on than perhaps any other, sometimes even as /uu/ or /ou/, but these two variations are less frequent. The bare ⟨u⟩ marks that this final always triggers dentilabialization.
• The finals written ⟨un⟩ and ⟨ut⟩ in this notation are are usually reconstructed by scholars with a back and/or rounded vowel like [u]. They are usually rendered with -o instead of -u in earlier Japanese borrowings. These were considered good rhymes with the finals written here ⟨in⟩ ⟨it⟩, also without the macron. The bare ⟨u⟩ marks that these finals always trigger dentilabialization.
• All the finals written with macron ⟨ū⟩ in this notation exhibit vowel alternation in Kan-on. Like other finals written with U, they trigger dentilabialization, but not with initial ⟨m⟩.
  • The final ⟨(i)ū⟩ is usually reconstructed by scholars as a diphthong with some element of backness and roundedness, like [ɨu], [iu], or [iw]. The leading /i/ in on'yomi consistently disappears after labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩, so they are accordingly not written in these places. Like the ⟨(y)u⟩ finals, the vowel in these finals can be rendered unpredictably in Kan-on. In the syllable ⟨mū⟩, the vowel becomes /o/ in on'yomi, but it is written with U here to keep it visually distinct from ⟨mou⟩.
  • The finals ⟨(i)ūng⟩ ⟨(y)ūk⟩ are usually reconstructed by scholars with some element of frontness combined with some element of roundedness, such as [ɨuŋ], [iuŋ], or [iwŋ]. The leading /i/ and /j/ in on'yomi consistently disappear after labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩, so they are accordingly not written in these places. In the syllables ⟨mūng⟩ ⟨mūk⟩, the vowel becomes /o/ i on'yomi, but it is written with U here to keep it visually distinct from ⟨mōng⟩ and ⟨mōk⟩.
  • The finals ⟨yūn⟩ and ⟨yūt⟩ are in alternation with ⟨wīn⟩ and ⟨wīt⟩ respectively. These two finals are usually reconstructed by scholars with some element of frontness combined with some element of roundedness, as in [iuɪn] or [win], and in later stages of Middle Chinese, they involved a simple vowel that was simultaneously fronted and rounded, as in [yn].

The four rows of the rime tables [show contents]

I briefly mentioned above that one of the foundational sources for Middle Chinese phonology is something called the "rime tables". These tables were basically a tool used for looking up words' pronunciations, much like you might use a dictionary for today. But instead of writing out pronunciations in phonetic symbols somehow, the compilers of these tables invented a sophisticated grid system. They took every Chinese syllable they could think of, and chose one representative character for each. Then, they arranged these characters on a series of grids, grouping similar-sounding characters close together. It was a complex system, much more complex than you'll find in dictionaries today, but it was an ingenious system for the time. It made it possible for any Chinese speaker at the time to easily look up character readings, without having to learn any new writing system.

Of course, for us moderns, the principles behind this grid system are not always clear. We know that the 23 columns of each grid corresponded to characters' initial consonants. But the four rows in this grid system are perhaps the biggest mystery of Middle Chinese phonology. Scholars agree that they relate simultaneously to the initial consonants and the vowels of the various syllables in the rime tables. But beyond that, there's endless controversy around these rows. Where two scholars differ greatly in their reconstructions of a given syllable, it usually boils down to a difference in how they interpret the four rows.

The four rows of the rime tables feature in this notation in a few different ways, including the usage of diacritic marks.

• The underdot ⟨◌̣⟩ always shows up in syllables placed in the second row.
• The acute accent ⟨◌́⟩ and circumflex ⟨◌̂⟩ only show up in syllables placed in the third row.
• The grave accent ⟨◌̀⟩ and the bare letter E only show up in syllables placed in the fourth row.

There are many more ways that the various symbols in this notation relate to the four rows. But which row a syllable belongs to is not as important as another kind of grouping based on the rime tables, which is intimately connected to the four rows.

Marks of the "Four Divisions" of the rime tables [show contents]

Modern-day scholars studying the rime tables found some patterns relating to these four rows. Using these patterns, they grouped all the syllables of Middle Chinese into four categories, usually called the "Four Divisions" in English. (Confusingly, the four rows of the rime tables are also sometimes called divisions, but I will refer to them distinctly as "rows" and "Divisions" here.)

The details of these Four Divisions are complicated, but what's important to know is that two syllables belonging to the same Division probably had similar vowel sounds. Likewise, two syllables belonging to different Divisions probably had different vowel sounds. More is said on the possible phonetic features of these Four Divisions in the individual "finals" sections above.

Here is a summary of all the characteristic marks of the Four Divisions in this notation. Where a cell is greyed out, that means there are no syllables with that main vowel for that Division.

As you can see, there are some features of the Four Divisions that are clearly manifest in the Kan-on vowel. For instance, syllables containing /j/ a Y- sound in Kan-on, or one of the main vowels /i/ /u/, are invariably in Division III. Therefore, these syllables don't need a diacritic mark to distinguish them as such.

Marks of Kan-on/Go-on vowel alternation[show contents]

Earlier, we saw that the character 家 ⟨kạ⟩ has the on'yomi カ ka. This reading shows up in common words like 家族 kazoku "family". But there is another common reading ケ ke which predates カ ka, for example in the word 家来 kerai "servant". The readings belonging to this older set are called Go-on.

Go-on originate from a wave of borrowings into Japanese that happened early on in the Middle Chinese period. The Go-on readings were largely replaced by the Kan-on which form the basis for the vowels in this notation. Not all characters have an attested Go-on reading, but some Go-on readings are used in very common words, and are even more commonly used than their Kan-on counterparts in some cases.

As a Japanese learner, you don't need to know how to identify Kan-on vs. Go-on readings. This distinction is something that many Japanese speakers today are not aware of. However, when the Kan-on and Go-on readings of a character differ, you can often predict this variation by looking at the vowel in this Middle Chinese notation. For example:

There are even more patterns than these. This table is here not for you to memorize, but to illustrate a point: whenever you encounter a kanji whose on'yomi has a variable vowel sound, you can take a look at the kanji's Middle Chinese reading, and you can reasonably guess that other kanji with a similar-looking Middle Chinese reading just might exhibit the same kind of vowel alternation.

Most of the above diacritics serve other functions besides marking Kan-on/Go-on vowel alternations. You'll notice that many of the vowels above double as marks of the Four Divisions. For instance, ⟨ạ⟩ with underdot is a characteristic mark of Division II, and ⟨â⟩ with circumflex is a characteristic mark of Division III. The circumflex doubles as a mark of dentilabialization on preceding labial consonants ⟨p⟩ ⟨pʻ⟩ ⟨b⟩ ⟨m⟩.

Marks of vowel alternation within Kan-on[show contents]

Sometimes, one Middle Chinese final is rendered in a couple different ways in Kan-on. For example, the characters 筠 and 春 both probably had the exact same final at early stages of Middle Chinese, but in Kan-on, they are rendered with different vowels as 筠 win and 春 syun. This might be because, at the time of borrowing, the original Chinese vowel had split into two different vowels, or it may have been that the compilers of Kan-on just interpreted the vowel differently in these different instances. In any case, this sort of vowel alternation is sometimes incorporated into this notation. When this happens, the vowels subject to alternation are usually marked with some kind of diacritic—in the case of our example, the macron is used, giving 筠 ⟨wīn⟩ and 春 ⟨tśʻyūn⟩.

Here are all the patterns of Kan-on vowel alternation that were incorporated into this notation.