Senryū (川柳, literally 'river willow') is a Japanese form of short poetry similar to haiku in construction: three lines with 17 morae (or "on", often translated as syllables, but see the article on onji for distinctions). Senryū tend to be about human foibles while haiku tend to be about nature, and senryū are often cynical or darkly humorous while haiku are more serious. Unlike haiku, senryū do not include a kireji (cutting word), and do not generally include a kigo, or season word.