haiku, unrhymed poetic form consisting of 17 syllables arranged in three lines of 5, 7, and 5 syllables respectively. The haiku first emerged in Japanese literature during the 17th century, as a terse reaction to elaborate poetic traditions, though it did not become known by the name haiku until the 19th century.

The term haiku is derived from the first element of the word haikai (a humorous form of renga, or linked-verse poem) and the second element of the word hokku (the initial stanza of a renga). The hokku, which set the tone of a renga, had to mention in its three lines such subjects as the season, time of day, and the dominant features of the landscape, making it almost an independent poem. The hokku (often interchangeably called haikai) became known as the haiku late in the 19th century, when it was entirely divested of its original function of opening a sequence of verse. Today the term haiku is used to describe all poems that use the three-line 17-syllable structure, even the earlier hokku.

Originally, the haiku form was restricted in subject matter to an objective description of nature suggestive of one of the seasons, evoking a definite, though unstated, emotional response. The form gained distinction early in the Tokugawa period (1603–1867) when the great master Bashō elevated the hokku to a highly refined and conscious art. He began writing what was considered this “new style” of poetry in the 1670s, while he was in Edo (now Tokyo). Among his earliest haiku is

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The Literary World

On a withered branch
A crow has alighted;
Nightfall in autumn.

Bashō subsequently traveled throughout Japan, and his experiences became the subject of his verse. His haiku were accessible to a wide cross section of Japanese society, and these poems’ broad appeal helped to establish the form as the most popular form in Japanese poetry.

After Bashō, and particularly after the haiku’s revitalization in the 19th century, its range of subjects expanded beyond nature. But the haiku remained an art of expressing much and suggesting more in the fewest possible words. Other outstanding haiku masters were Buson in the 18th century, Issa in the late 18th and early 19th centuries, Masaoka Shiki in the later 19th century, and Takahama Kyoshi and Kawahigashi Hekigotō in the late 19th and early 20th centuries. At the turn of the 21st century there were said to be a million Japanese who composed haiku under the guidance of a teacher.

A poem written in the haiku form or a modification of it in a language other than Japanese is also called a haiku. In English the haiku composed by the Imagists were especially influential during the early 20th century. The form’s popularity beyond Japan expanded significantly after World War II, and today haiku are written in a wide range of languages.