The word waka has two different but related meanings: the original meaning was "poetry in Japanese" and encompassed several genres such as chōka and sedōka (discussed below); the later, more common definition refers to poetry in a 5-7-5-7-7 metre. Up to and during the compilation of the Man'yōshū in the eighth century, the word waka was a general term for poetry composed in Japanese, and included several genres such as tanka (短歌, "short poem"), chōka (長歌, "long poem"), bussokusekika (仏足石歌, " poem") and sedōka (旋頭歌, "repeating-the-first-part poem"). However, by the time of the Kokinshū's compilation at the beginning of the tenth century, all of these forms except for the tanka and chōka had effectively gone extinct, and chōka had significantly diminished in prominence. As a result, the word waka became effectively synonymous with tanka, and the word tanka fell out of use until it was revived at the end of the nineteenth century (see Tanka).
Tanka (hereafter referred to as waka) consist of five lines (句 ku, literally "phrases") of 5-7-5-7-7 on or syllabic units. Therefore, tanka is sometimes called Misohitomoji (三十一文字), meaning it contains 31 syllables in total.