The Forms of the Infinitive

	Active	Passive
Indefinite	to teach	to be taught
Continuous	to be teaching	to be being taught
Perfect	to have taught	to have been taught
Perfect Continuous	to have been teaching	---

The Indefinite Infinitive expresses an action simultaneous with that expressed by the finite verb.
E.g.: I shall be glad to see him.

The Continuous Infinitive denotes an action in progress simultaneous with that expressed by the finite verb.
E.g.: He seemed to be waiting for us.

The Perfect Infinitive denotes an action prior to that expressed by the finite verb.
E.g.: I am sorry to have troubled you.

The Perfect Continuous Infinitive denotes an action which lasted a certain time before the action of the finite verb.
E.g.: He proved to have been teaching English for ten years.

The Active Infinitive denotes that the subject is the doer of the action.
The Passive Infinitive denotes that the subject is acted upon.
E.g.: The man came to teach us English.
         The man came to be taught English.
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