upper bigrade conjugation; nidan verb conjugation (classical Japanese)
A classical Japanese verb conjugation class where the stem vowel alternates between /i/ and /u/ across forms. Modern Japanese verbs that were originally 上二段 have mostly shifted to 上一段 (upper monograde) conjugation.
Upper bigrade conjugation is a verb conjugation studied in classical grammar.
Upper bigrade conjugation is a conjugation where the irrealis form ends in the /i/ row, the continuative form ends in the /i/ row, and the terminal form ends in the /u/ row.
Compound of 上 (kami, 'upper', referring to the /i/ vowel row) + 二段 (nidan, 'two grades') + 活用 (katsuyō, 'conjugation'). The term describes a classical conjugation pattern with two stem vowels in the upper (i-row) and middle (u-row) grades.