On (音) is Japanese for "sound". It is used to mean the phonetic units counted in haiku, tanka and other such poetic forms. Known as "morae" to English-speaking linguists, the modern Japanese term for the linguistic concept is hyōon moji (表音文字).[1]
Ji (字) is Japanese for "symbol" or "character". The concatenation of the two words on and ji into onji (音字), was used by Meiji era (1868–1912) grammarians to mean "phonic character" and was translated into English by Nishi Amane in 1870 as "letter". Since then, the term has become obsolete in Japan, and only survives in foreign-language discussion of Japanese poetry. Gilbert and Yoneoka [2] call the use of the word onji "bizarre and mistaken". It was taken up after a 1978 letter to Frogpond: Journal of the Haiku Society of America decrying the then-current use of the word jion, which itself appears to have arisen in error.[3][4] The normal Japanese term in the context of counting sounds in poetry is "on".[3]
Counting on in Japanese poetry is the same as counting characters when the text is transliterated into hiragana. In cases where a hiragana is represented by a pair of symbols each pair (or "digraph" e.g. "kyo" (きょ)) equates to a single on. When viewed this way, the term "ji" ("character") is used in Japanese.[3]
In English-language discussions of Japanese poetry, the more familiar word syllable is sometimes used. Although the use of "syllable" is inaccurate, it often happens that the syllable count and the on count match in Japanese-language haiku. The disjunction between syllables and on becomes clearer when counting sounds in English-language versions of Japanese poetic forms, such as haiku in English. An English syllable may contain one, two or three morae and, because English word sounds are not readily representable in hiragana, a single syllable may require many more ji to be transliterated into hiragana.
To illustrate this, the most famous of all haiku, Bashō's
happens to contain 17 monomoraic syllables (i.e. it has 17 morae or hyōon moji, 17 syllables and 17 on or ji), while the English phrase
contains three syllables but six morae. An attempted transliteration of that phrase into hiragana would require at least ten ji.
There is disagreement among linguists as to the definitions of "syllable" and "mora".[5] In contrast ji (and hence on) is unambiguously defined by reference to hiragana.