nidan verb with 'u' ending (archaic), intransitive verb
to be possible; to be conceivable; to be likely
Archaic Nidan verb form of modern あり得る (ありえる). Used in classical Japanese to express possibility or likelihood. Not used in modern speech; learners will encounter it only in historical texts.
See also: ありえる
古典では「有り得」と書いて「ありう」と読むことがある。
In classical texts, 有り得 is sometimes read as ありう.
「ありうべきこと」という表現が古い文章に見られる。
The expression ありうべきこと (something that could be) is found in old writings.