In English grammar, the uninflected verb-form used in a number of clause types: imperative ('Go away'), subjunctive ('We recommend she go away'), and infinitival ('We should go away', 'We want her to go away'). There are some grounds for distinguishing it from the finite, non-third-singular present form ('We go away tomorrow'), even though they are formally identical in all verbs except 'be'. (And there are some grounds for treating them as the same.) English verbs do not have imperative, subjunctive, or infinitive forms: they have a single plain form used in clauses of those types.
The term is also used in Japanese grammar for the ordinary non-polite form.