A grammar word. English verbs usually carry two pieces of information at once: WHO does it, and WHEN. "She goes" tells you the doer is she, and the time is now. "She went" tells you the time is past. That kind of verb form is called finite — it is fixed, or limited, to one subject and one time. A non-finite verb form does none of that. It is the verb with no time and no doer attached to it. English has three of them: the infinitive ("go", "to go"), the -ing form or present participle ("going"), and the past participle ("gone"). Look at "Do you want to go home?" — the word that carries the tense is "do", not "go". "Go" just sits there, timeless. Change it to "Did you want to go home?" and "go" still does not move. That is the test teachers use: if the sentence changes time and the verb form stays the same, that verb is non-finite. This is a technical term, used by grammar books, language teachers and exam papers. You will almost never hear it in ordinary conversation, and native speakers who are not teachers often do not know it — that is normal, and it does not mean they use the grammar badly. It is useful to you mostly as a label: it names the reason why we say "I want to eat" and never "I want to eats". After certain verbs, prepositions, and helping verbs, English demands the timeless form. Some books also say "non-finite clause" for a chunk built around one of these forms, like "Having finished her work, she left." Written both with and without the hyphen — "nonfinite" is common in American academic writing.

非限定（動詞）；台灣文法書多寫「非限定動詞」或「非定式動詞」，跟 finite「限定動詞」對著看。要注意「限定」在這裡不是「限制數量」的意思，而是「被主詞和時態框住」——沒被框住的就是 non-finite。學校課本講「不定詞、動名詞、分詞」時，講的其實就是這一類。