An Overview of Spanish Infinitives:

The infinitive is the "bare" form of the verb. It provides information about meaning, but not grammar (no information about the subject, the tense or the number). The ending does provide information, however, about the possible forms the verb can take. The three main infinitive verbs are -ar verbs (e.g.: hablar), -er verbs (e.g.: vender) and -ir verbs (e.g.: salir).

In terms of usage, the infinitive is used:

a) after prepositions, e.g.: Acabo de hablar con los niños.

b) after other verbs, like poder, querer, necesitar and ir, e.g.: Puedo venir con ustedes.

c) alone as a noun, e.g.: Leer es vivir.

• The infinitive does not follow forms of the verbs ser, estar or haber;
• The infinitive does not follow subjects (like yo, tú, etc.)