Definition of 'Infinitive verb' The infinitive is the pure form of a verb is usually used to refer to the "to + verb" form of the verb such as "to sleep" or "to work," In Spanish, infinitives always end in -ar, -er or -ir, with -ar being the most common. Other examples of infinitives in Spanish are comer, viajar, comprender, and practicar. The corresponding English infinitives are "to eat," "to travel," "to understand," and "to practice." Using Infinitives the same way like E