noun
yodan verb conjugation; classical Japanese verb conjugation
Linguistics term for the four-grade verb conjugation pattern of classical Japanese, the predecessor of modern godan (五段) verbs.
See also: 五段活用
In classical Japanese grammar, yodan conjugation has six inflected forms: mizen, ren'yō, shūshi, rentai, izen, and meirei.
「書く」は四段活用の動詞で、未然形は「書か」、連用形は「書き」となる。
'Kaku' (to write) is a yodan verb; its mizenkei is 'kaka' and its ren'yōkei is 'kaki'.