The Japanese poem form traditionally associated with 17 syllables is haiku. In its classical Japanese pattern, a haiku has three phrases containing 5, 7, and 5 morae, sound units that are not exactly the same as English-language syllables.
Haiku developed from hokku, the opening stanza of the collaborative linked-verse form renga. Japanese poets eventually wrote hokku as independent poems, and the writer Masaoka Shiki gave the form its modern name, haiku, near the end of the 19th century. Traditional haiku commonly include a kigo, or seasonal reference, and a kireji, or cutting word that creates a pause or shift.
The phrase “17 syllables” is a useful shortcut, especially in introductory quizzes, but it can mislead readers writing in English. Japanese counts morae, while English haiku often use flexible line lengths and do not always follow 5–7–5. Matsuo Bashō, one of the best-known classical haiku poets, sometimes departed from the standard pattern. Short Japanese poems without the traditional haiku conventions may instead be classified as senryū, particularly when they focus on human behavior or humor.