trigrade conjugation; three-grade conjugation
A classical Japanese verb conjugation pattern where the stem vowel alternates between i, u, and o. Applies to certain verbs ending in す or く in classical grammar. A technical term used in grammar study.
In classical grammar, '死ぬ' is a na-row irregular conjugation, and 'す' is considered a type of trigrade conjugation.
In trigrade conjugation, the mizenkei is on the 'i' row, the renyōkei on the 'i' row, the shūshikei on the 'u' row, the rentaikei on the 'u' row, the izenkei on the 'o' row, and the meireikei on the 'o' row.
Quadrigrade conjugation, where the stem vowel alternates between a, i, u, and e. More common than trigrade conjugation in classical verbs.
Bigrade conjugation, with stem vowels alternating between two rows (e.g., i and u, or e and u).
Irregular conjugation, such as カ行変格活用 (k-irregular) or サ行変格活用 (s-irregular).
From 三段 (three grades) + 活用 (conjugation), referring to the three vowel rows (i, u, o) used in the conjugation pattern.