A verb-phrase made by prefixing to have to the past participle is called the perfect infinitive.

I am sorry to have missed you.

245. Three forms of the verb are so important that they are called the principal parts. These are:—

PresentPastPast Participle
(I) walk(I) walkedwalked
(I) think(I) thoughtthought
(I) see(I) sawseen
(I) come(I) camecome
(I) make(I) mademade

VOICE—ACTIVE AND PASSIVE

246. Voice is that property of verbs which indicates whether the subject acts or is acted upon.

There are two voices, active and passive.

1. A verb is in the active voice when it represents the subject as the doer of an act.