An infinitive is a form of a verb that does not completely specify person, number, tense, mood, aspect, and voice. That is, an infinitive cannot function as a finite verb, that is, as the main verb in a sentence. Instead, the infinitive can function as a verbal noun or can be combined with one or more auxiliary verbs to form a compound finite verb.
Infinitive verbs are often identified in the English language by a preceding "to" before the base form (i.e., to go, to work, to edit); this is known as a full infinitive. An infinitive with any words between the "to" and the base form (e.g., "to boldly go") is called a split infinitive. While many people believe that split infinitives are ungrammatical, some authorities disagree.