The Form of Infinitives
So far you have been exposed to two infinitives (the present active and present passive) and one infinitive use (complementary). There are, in fact, six infinitives and four infinitive uses. Don't worry. Once again you will see that this is mostly stuff you already know, but didn't know you knew!
The six infinitives comprise three tenses and two voices. The tenses are present, perfect, and future; the voices are, of course, active and passive. This matrix should sound familiar. Participles are organized the same way. Infinitives, however, don't leave any blank spaces in their chart.
Table 17-1 Infinitives
Take a good look at the forms on this chart and examine the tenses that you have learned.
Present active: the second principle part of a verb
Present passive: short e changes to an ī
Perfect active: pluperfect subjunctive active without personal endings (perfect active stem plus -isse)
Perfect passive: pluperfect subjunctive passive without personal endings (perfect passive participle with esse)
Future active: future active participle with esse
Future passive: supine with ī rī(ī rībeing the only new form for you to learn in this chapter!)
The future active infinitive usually appears without the esse. It is also important to know that the future active infinitive of sum, futū rus esse, quite often appears as fore. Furthermore, fore is also sometimes used in place of esse, especially in forming the imperfect subjunctive of sum; for example, forem for essem, et cetera.