Kigo, season word or kidai, seasonal topic (in haiku poetry) is a word symbolizing a given season and it is considered desirable that one of either kigo or kidai be contained in a haiku poetry.
季語（きご）あるいは季題（きだい）は、俳句に必ず1つ含まれることが望ましいとされる、季節を象徴的に示す語。