Uses of the Infinitive

• To complete a sentence with a helping verb. Eg. ire volumus we want to leave; haberi cupit he wants to be held
• As a subject of a verb. Eg. id invenire difficile est to find it is difficult
• As a direct object. Eg. natare amat he likes to swim
• In an indirect statement, after verbs such as "say," "think," "know," or "hear."
  • If the action of the indirect statement takes place at the same time as the action of the main verb, use the present infinitive. Eg. mulierem discedere credo I believe the woman is leaving.
  • If the action of the indirect statement takes place before the action of the main verb, use the past infinitive. Eg. mulierem discerisse credo I believe the woman has left
  • If the action of the indirect statement takes place after the action of the main verb, use the future infinitive. Eg. mulierem discessura esse credo I believe the woman will leave
  • Note that the subjects of infinitives take the accusative, and the perfect passive and future active infinitives are also declined in the accusative, matching the gender and number of their subjects as well.