The shortest waka type, katauta, follows a 5-7-7 sound pattern.
Katauta means “half-poem.” It was traditionally used as one half of a poetic exchange, with a second katauta completing the thought or response. Its three units contain five, seven, and seven on, or sound units, respectively.
Katauta belongs to the older range of Japanese waka forms preserved especially in early literature such as the Man’yōshū. Other forms used different arrangements: tanka follows 5-7-5-7-7, sedōka uses 5-7-7-5-7-7, and chōka repeats 5-7 units before ending in 5-7-7.
A frequent mistake is to apply the familiar haiku pattern, 5-7-5, to every short Japanese poem. Katauta is not haiku, and its final unit has seven sound units rather than five. Japanese “sounds” are more precisely counted as on or morae, so English syllable counts are only an approximation.