Haiku is a type of short form poetry that originated in Japan. Traditional Japanese haiku consist of three phrases composed of 17 phonetic units in a 5, 7, 5 pattern; that include a kireji, or "cutting word"; and a kigo, or seasonal reference. However, haiku by classical Japanese poets, such as Matsuo Bashō, also deviate from the 17-on pattern and sometimes do not contain a kireji. Similar poems that do not adhere to these rules are generally classified as senryū.
Haiku by Matsuo Bashō reading "Quietly, quietly, / yellow mountain roses fall – / sound of the rapids"
Grave of Yosa Buson
A kigo is a word or phrase associated with a particular season, used in traditional forms of Japanese poetry. Kigo are used in the collaborative linked-verse forms renga and renku, as well as in haiku, to indicate the season referred to in the stanza. They are valuable in providing economy of expression.
Cherry blossoms (sakura), often simply called blossoms (hana) are a common spring kigo.
The moon is associated with autumn in Japanese poetry.
A sunflower, a typical summer kigo.
The cicada (semi) is a common late summer kigo.