literary form; classical Japanese word form
A grammatical term referring to the inflected or base form of a word as used in classical Japanese (文語), such as あり, 速し, or 静かなり. Contrasts with 口語形 (colloquial/modern form).
See also: 口語形
「あり」 is the classical literary form of 「ある」.
In classical Japanese, you need to memorize the literary forms of adjectives.
Compound of 文語 (literary language) + 形 (form).