noun
subsidiary verb; auxiliary verb
A grammatical term for verbs that attach to the te-form of another verb to add grammatical meaning such as aspect, direction, or benefactive nuance. Common examples include いる, ある, いく, くる, しまう, おく, みる, くれる, あげる, もらう.
「〜ている」の「いる」は補助動詞です。
The いる in 〜ている is a subsidiary verb.
補助
Subsidiary verbs need to be taught separately from main verbs.
本動詞 is a main verb used with its full lexical meaning, while 補助動詞 is a grammaticalized verb that follows a te-form and adds functional meaning.
助動詞 are bound auxiliary morphemes that attach to verb stems or other forms (e.g., 〜れる, 〜たい), whereas 補助動詞 are independent verb forms that follow te-forms.
Compound of 補助 (hojo, 'assistance, support') and 動詞 (dōshi, 'verb'). The term is a modern linguistic coinage for describing Japanese grammar.