Onbin

Sound changes such as "Kite" becoming "Kaite" , "Takaki" becoming "Takai" , "Hayaku" becoming "Hayau" , "Torite" becoming " Totte" , and "Tobite" becoming "Tonde" (losing of consonants and vowels, assimilation and change of consonants) are called "onbetsu". They often occur at the end of the upper word when two words are compounded, and are divided into the following four types.

(1) I-sound change (ki, gi, shi etc. become i) kisai ← kisaki, koide ← kogite, maite ← mashite
(2) U-sound change (Ku, Gu, Hi, Bi, Mi, etc. become U) Hayau ← Hayaku, Kaubashi ← Kagubashi, Koute ← Please, Youde ← Yobite, Tanoude ← Please,
(3) The sound of the beat (ni, bi, mi, ri, etc. become n) Shinde ←Shinitesu, Tonde ←Tobitesu, Yonde ←Yomimitesu, Sakanni ←Moririni
(4) Glottal stop (chi, hi, ri, etc. become tsu) tatte ←tachite, otte ←oihite, atte ←aririte In modern times, there are cases where the phonetic stop forms that arose in ancient times have been fixed and are used ( taimatsu [torch]←takimatsu, kaugai [hairpin]←kamigaki), and cases where both the phonetic stop forms and the original forms are used, such as in the conjunctive forms of verbs and adjectives. The latter can be said to be living phonetic stop forms, but in these cases, one cannot freely choose between the phonetic stop forms and the non-phonetic stop forms (this is different from the Heian period, etc.). In other words, in modern times, when the conjunctive form of a four-step verb (excluding the sa row) is followed by the particle "te" or "tari" or the auxiliary verb "ta", the phonetic stop forms are always used, while in cases such as "kakumazu" ( write ) and "yoku asobi yoku manabe" ( play well and learn well), the non-phonetic stop forms are always used. The phonetic form of the conjunctive adjective is not used in modern standard Japanese (Tokyo dialect) except for expressions such as "Good morning" and "It's hot," but it is widely used in the Western Japanese dialect. Also, whether "Kaite" and "Aite" are pronounced as "kaute" (→ kote) or "aute" (→ ote) or "katte " or "atte" differs between Western and Eastern Japan.

Examples of sound change were rare in the ancient period, and it became common in the Heian period, but the use of sound change forms was avoided in waka poetry until very recently. The cause of sound change has traditionally been said to be "for convenience of pronunciation," but this does not explain why "writer" and "rower" do not become "kaite" and "koide." Also, unlike 4-step verbs, jo-ni-dan verbs do not undergo sound change (for example, they are said as "oite" but not as "oite"), and this has not been resolved. There has long been a theory that the sound of Chinese characters may have influenced the emergence of sound change, but this is not conclusive.

[Yasuda Naomichi]

Source: Shogakukan Encyclopedia Nipponica About Encyclopedia Nipponica Information | Legend

書キテがカイテ、高キがタカイ、早クがハヤウ、取リテがトッテ、飛ビテがトンデとなるような音変化（子音・母音の脱落、子音の同化・変化）を音便とよぶ。2語が複合した場合の上の語の末尾に生ずることが多く、次の4種に分けられる。

(1)イ音便（キ・ギ・シなどがイとなる）　キサイ←后(キサキ)、コイデ←漕(コ)ギテ、マイテ←マシテ
(2)ウ音便（ク・グ・ヒ・ビ・ミなどがウとなる）　ハヤウ←早ク、カウバシ←カグハシ、コウテ←請ヒテ、ヨウデ←呼ビテ、タノウデ←頼ミテ
(3)撥(はつ)音便（ニ・ビ・ミ・リなどがンとなる）　シンデ←死ニテ、トンデ←飛ビテ、ヨンデ←読ミテ、サカンニ←盛リニ
(4)促音便（チ・ヒ・リなどがッとなる）　タッテ←立チテ、オッテ←追ヒテ、アッテ←有リテ
　現代では、古い時代に生じた音便形が固定化して用いられている場合（タイマツ〔松明〕←焚(タ)キ松、カウガイ〔笄〕←髪掻(カミガ)キ）と、動詞・形容詞の連用形のように音便形と元の形の両方が用いられる場合とがある。後者はいわば生きている音便とでもいうべきものだが、この場合、音便形・非音便形のいずれかを自由に選んで使うということはできない（この点が平安時代などと違う）。すなわち、動詞は、現代では四段動詞（サ行を除く）の連用形に助詞「て」「たり」や助動詞「た」がつく場合はかならず音便形を、「書きます」「よく遊びよく学べ」のような場合はかならず非音便形を用いるのである。形容詞の連用形の音便形は、現代の共通語（東京語）では、「お早うございます」「暑うございます」のような言い方以外には用いないが、西日本方言では広く用いる。また、「買ひて」「会ひて」がカウテ（→コーテ）、アウテ（→オーテ）となるか、カッテ、アッテとなるかも、西日本と東日本とで分かれる。

　上代には音便の例はまれで、一般化するのは平安時代だが、和歌においてはのちのちまで音便形の使用は避けられた。音便発生の原因については、従来、「発音の便宜から」とされてきたが、これでは、「書き手」「漕ぎ手」がカイテ、コイデとならないことの説明ができない。また、四段動詞と違って上二段動詞は音便をおこさない（たとえば、置(オ)イテとはいうが起(オ)イテとはいわない）のはなぜかといったことも解決がついていない。音便の発生には漢字音の影響があろうとする説も古くからあるが、確定的ではない。

［安田尚道］

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