Haiku (俳句, listenⓘ) is a type of short form
poetry that originated in Japan. Traditional
Japanese haiku consist of three phrases composed
of 17 morae (called on in Japanese) in a 5, 7, 5
pattern;[1] that include a kireji, or "cutting
word";[2] 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.[3]
source :
https://en.wikipedia.org/wiki/Haiku
