A traditional tanka poem has 31 sound units, commonly described in English as 31 syllables. Its classic pattern is 5–7–5–7–7, arranged as five metrical units. The first three units form the upper section, while the final two create the closing 7–7 movement.
Tanka is one of Japan’s oldest major short-poem forms. It developed from waka traditions and appears prominently in classical anthologies, including the Man’yōshū and the Kokinshū. The form was often used for personal expression, especially love, longing, travel, seasonal observation, and courtly communication.
There is an important technical nuance: Japanese poetry traditionally counts morae, or sound units, rather than English-style syllables. “Thirty-one syllables” is therefore a convenient approximation used in general-audience explanations. Classical poets could also vary the standard count. A tanka that runs long is called ji-amari, while one that falls short is ji-tarazu. The term tanka was revived in modern usage by Masaoka Shiki, who also helped modernize the related haiku tradition.