Phonology IV: 露出形 & 被覆形
The final vowel in a native morpheme tends to alternate between two forms: one form which is used when the morpheme is in isolation and another form for which is used in compounds but only if said morpheme is the first element. For instance, 雨 meaning “rain” is あめ as a standalone noun, but it manifests as あま in compounds such as 雨雲（あまぐも）. This lesson will try to shed led on how exactly these alternating forms work.
露出形 & 被覆形
To begin, let’s consider the word 白玉, which is read as しらたま. The しろ reading of 白 is known as its 露出形, whereas its しら reading is known as its 被覆形. It turns out that there are three such vowel shifts between these so-called forms.
| i―o | き + かげ → 木陰（こかげ) Tree shade |
| e―a | め + ふた → 瞼（まぶた） Eyelid |
| o―a | くろ + やみ → 暗闇（くらやみ） Darkness |
As we go through how these sound changes work, it must be noted that what is being discussed are, at best, rule-bound instances but which may ultimately not affect every word made by the morphemes involved. Though this may be viewed as an erosion of this traditional feature of Japanese phonology, 白, for instance, may frequently be read as しろ even in compounds such as 白熊（しろくま）.
I―O/U
/i/ which change to /o/ in their 被覆形 are thought to have been rendered as a vowel closer to [ï] in their 露出形 in pre-Old Japanese.
| kï + tati → kodati こだち (木立) Grove of trees |
| kï き + no の + ma ま → konoma このま (木の間) In the trees |
| tukï つき + yo よ → tukuyo つくよ (月夜) Moonlit night |
| pï ひ + teru てる → poteru ほてる (火照る) To feel hot |
| kutï くち + wa わ → kutuwa くつわ (轡) Bit |
| kami かみ + agari あがり → kamuagari (神上り) Ascension of a kami |
Rather than positing that the 被覆形 is the derived form, there is also the analysis that the 露出形 is the combination of the 被覆形 plus an affix, dubbed /-i/ which attached and fused to give the freely standing 露出形.
The existence of this morpheme /-i/ is posited due to instances of it not being fused to the preceding noun in various instances in Old Japanese literature.
1.
忍坂の大室屋に人多に來入り居り人多に入り居りとも
厳厳し 久米の子が頭槌い 石槌い持ち 撃ちてし止まむ
厳厳し 久米の子等が頭槌い 石槌い持ち 今撃たば宜し
A lot of people have come to the big cellar in Osaka. Even a lot of people were to enter, are the vigorous Kumebe not going to hit at their enemies with their war and stone hammers? It would be best for the vigorous Kumebe to strike them with their war and stone hammers now!
From the 古事記.
2. 菟原壮士い 天仰ぎ
The man Urai looked up at the heavens
From the 万葉集.
In Ex. 1, /-i/ appears to function as an instrumental case marker much like で does today, but in Ex. 2, it appears to function as a subject marker. In an attempt to view these instances as one of the same thing, /-i/ may be viewed as marking “definitiveness,” much like “the” does in English but in the mind frame of providing clarity about the most important constituent of the predicate1.
If /-i/ did indeed fuse itself with countless nouns in Japanese, this would have been borne from a propensity to favor the importance of one noun in a sentence, and with any noun potentially fitting that role, that “definite” form became the 露出形 for those nouns.
It is also believed that this same morpheme /-i/ may have given rise to the 連用形 of verbs, which would provide a reasoning for why that base has a nominalizing effect. /-i/ is even seen after the 連用形 in the phrase 或いは (perhaps), which utilizes the existential verb あり (to be). Here, we see the same nominalizing effect that /-i/ has paired with the topic marker は.
E―A
It is thought that the merger of the aforementioned morpheme /-i/ and preceding /a/ gave rise to the Old Japanese vowel e2,2 which resulted in most instances of the vowel /e/ in Modern Japanese.
| 掌 | たなごころ | Palm | 手綱 | たづな | Rein |
| 船大工 | ふなだいく | Boat-builder | 爪弾き | つまはじき | Ostracism |
| 船酔い | ふなよい | Seasickness | 爪楊枝 | つまようじ | Toothpick |
| 胸算用 | むなざんよう | Anticipation | 金物 | かなもの | Metal utensil |
| 胸毛 | むなげ | Chest hair | 上の空 | うわのそら | Absent-mindedness |
| 声音 | こわね | Tone of voice | 風上 | かざかみ | Windward |
| 酒屋 | さかや | Liquor store | 風下 | かざしも | Leeward |
| 眉毛 | まゆげ | Eyebrow | 睫（毛） | まつげ | Eyelash |
| 天の川 | あまのがわ | Milky Way | 天の浮橋 | あまのうきはし | Heavenly floating bridge |
| 雨傘 | あまがさ | Umbrella | 菅原 | すがわら | Sugawara (surname) |
| 猪苗代 | いなわしろ | Inawashiro (Place name) | 苗水 | なわみず | Water for rice nursery |
Etymology Note: 天 and 雨 are ultimately etymologically identical.
Exceptionally, 白髪 is read as しらが instead of しらげ, but this is because it is a contraction of しらがみ at a later stage.
It turns out that the /-i/ morpheme also combined itself to a handful of adjectival roots, providing word forms such as 飴 (candy) and 岳 (peak) from the adjectival roots 甘 (sweet) and 高 (tall) respectively. Other evidence for this nominalizing イ is found in 或いは (possibly). When after the 連体形 of verbs, it showed a focus. As for these nouns, however, this would have been a grammatically necessary add-on to be used.
Consonant Deletion Before /-i/
For some instances of /-i/, it appears that a consonant is present/lacking between seemingly related pairs of words, in which /-i/ does seem to clearly play a role. For instance, 端（は） meaning “edge”3 appears to be an irregular case of a 露出形 in isolation, as there is also 辺（へ） meaning “side” as in a shore or surrounding area. Here, we see a semantic role /-i/ has in adding definitiveness to the noun.
At the same time there also exists the word form 端（はし）with the same meaning of “edge.” Some have posited that in instances in which /-i/ did not fuse with the preceding vowel, a consonant which only appeared at the end of the stem of the noun would appear with it, much like what frequently happens in Korean.
| Consonant Insertion in 露出形 | 被覆形 |
| ハ + s + イ → 端 | 端数（はすう） Fraction |
| ア + s + イ → 足 | 足掻（あが）く To struggle |
| クス + r + イ → 薬 | 薬師（くすし） Doctor (Archaism) |
| ト + r + イ → 鳥 | 鳥羽（とば） Toba |
| カタ + t + イ → 形 | 形見（かたみ） Memento |
| カガ＋m ＋ イ → 鏡 | |
| カ＋m ＋ イ → 髪 |
O―A
This 露出形・被覆形 relationship is not as common, but examples are presumably still tied to the morpheme /-i/.
| 白髪 | しらが | White/grey hair | 暗がり | くらがり | Darkness |
Instances of this are scattered, but the most interesting one is しな・しの “celestial body,” a word which still pops up in Okinawan languages but which did not survive into even Middle Japanese.
3. しなてる片岡山に、飯に飢て臥せる、その旅人あわれ。
That poor traveler who is faced down starved of food at Kataoka Mountain, illuminated by the light in the sky.
From a Song by 聖徳太子.
露出形 in Compounds
In examples of the 露出形 seemingly being interchangeable with the 被覆形 inside compounds, the traditional 被覆形 tends to be favored nonetheless. This is the case for words like 風向き (wind direction) in which かぜむき is far rarer than かざむき. As another example, まなじり and めじり exist for “corner of the eye,” but the latter comes about much later. And, the original is still the most common.
Sometimes, a particular form may be avoided because the resulting word would be homophonous to an existing word. The one example that immediately comes to mind is 白身. This is the white of an egg or the white flesh of certain species of fish. This word is read as しろみ. It is not read as しらみ presumably because this word means louse (虱・蝨).
At times, the use of the proper 被覆形 over the 露出形 may result in a change in meaning, but when this occurs, the choice is arbitrary in nature.
| 白魚 | しらうお ＝ Icefish | しろうお ＝ Ice goby |
Loss of 被覆形
There have been some words where the 被覆形 has essentially disappeared from the language. This is not surprising as not all words share this kind of phenomenon.
| 露出形 | 被覆形 | Now | |
| 身 | み | む | み |
| 茎 | くき | くく | くき |
| 藻 | め | も | も |
As the last example shows, the 被覆形 becoming the standalone variant is not unheard of. Of course, there are still examples of rare words where older forms may still be present.
- The true nature of the /-i/ morpheme is shrouded in mystery mostly due to how most instances of it did result in vowel fusing, leaving the prospect of instances in which it is not like in Exs. 1-2 being exceptional for the time but perhaps a regular occurrence before fusion occurred in earlier stages of the language. Parallels have been drawn with /-i/’s behavior to the subject marker /i/ found in Korean. ↩︎
- The vowel e2 is noted in Japanese literature as エ乙, but its exact pronunciation is uncertain. ↩︎
- 刃 (blade), 歯 (tooth), and 葉 (leaf) are all thought to be etymologically related. ↩︎