Meaning of 不定詞 in Japanese

needless to sayは不定詞の慣用表現として紹介されることが多いです。
'needless to say' is often introduced as an idiomatic expression in the infinitive.

次の動詞はｔｏ不定詞だけを目的語にとります。
The following verbs only take the to-infinitive as their object.

toのつかない不定詞を原形不定詞と言う。
An infinitive without a 'to' attached is called a bare infinitive.