This form of poetry, which has a five-line poem with the 5-7-5-7-7 syllable structure (thirty-one moras), was given different names in relation to the longer forms of poetry of the period.
五・七・五・七・七の五句体（31モーラ）の詩形は、その時代に盛んであった長い詩形との関連で呼び名が変わった。