listen is a form of Japanese poetry. Previously called hokku, it was given its current name by the Japanese writer Masaoka Shiki at the end of 19th century. Shiki suggested haiku as an abbreviation of the phrase "haikai no ku" meaning a verse of haikai, although the term predates Shiki by some two centuries, when it was used to mean any verse of haikai. A hokku was the opening verse of the collaborative linked verse form, renku (haikai no renga). In Japanese, hokku and haiku are traditionally printed in one vertical line. In English, haiku are usually written in three lines to equate to the three metrical phrases of a haiku in Japanese, which consist of five, seven, and five on (Japanese sound units equivalent to morae). Since the Japanese language does not distinguish between singular and plural in nouns, the word 'haiku' usually remains unchanged in its English plural form. Senryū is a similar poetry form that emphasizes irony, satire, humor, and human foibles instead of seasons, and may or may not contain a kigo or a kireji.

Kireji and kigo

Main articles Kireji, Kigo

In Japanese haiku a kireji (i.e. a cutting word) appears at the end of one of the three phrases. In Japanese, there are actual kireji words, which act as a sort of spoken punctuation (for example, the "ya" in Bashō's "furuike ya" poem is a kireji). In English, kireji has no direct equivalent. Instead, English-language poets often use commas, dashes, ellipses, or implied breaks to divide the three lines into two grammatical and imagistic parts. Such a division is usually placed at the end of either the first or second line; very rarely they can be found in the middle of the second line. The purpose is to create a juxtaposition, which creates space for an implication as the reader intuits the relationship between the two parts.

A haiku traditionally contains a kigo (season word) which symbolises or intimates the season in which the poem is set.

Among traditionalist Japanese haiku writers, both kireji and kigo are considered absolute requirements for the form, yet, as noted above, kireji are not in use in English. Season words (kigo), although considered by many to be essential to haiku, are not always included by modern writers of Japanese "free-form" haiku and some non-Japanese haiku.

Syllable or "on" in haiku

While English verse is typically characterized by meter, which counts "beats", Japanese verse instead typically counts sound units (morae), known in Japanese as "on". The word on is often translated loosely (and somewhat inaccurately) as "syllables", but there are subtle differences between an "on" and a "syllable". The traditional haiku consisted of a pattern of 5, 7, and 5 on.

The Japanese word on, literally "sound", corresponds to a mora, a phonetic unit similar but not identical to the syllable of languages such as English. (The word onji (音字; "sound symbol") is sometimes used in referring to the Japanese syllable units in English although this word is archaic and no longer current in Japanese. Richard Gilbert, Stalking the Wild Onji ) In Japanese, the on corresponds very closely to the kana character count (closely enough that Moji (or "character symbol") is also sometimes used as the count unit). One on is counted for a short syllable, an additional one for an elongated vowel or a doubled consonant (i.e., a glottal stop), and one for an added "n" at the end of a syllable. Thus, the word "sign", though one syllable in English, would be counted as three sounds if said in Japanese (sa-i-n).