Infinitive Overview and Formation
Table of contents
Infinitives Overview
Infinitives are verbal nouns. This means that while in terms of form, infinitives derive from verb dictionary entries, in usage, they can fulfill functions of a sentence like being a subject, an object of a preposition, etc. In English, the infinitive most often appears in the form “to [verb]”:
- The boy likes to dance.
- To err is human, but to forgive is divine.
Note that the infinitive (in- = “not”, Latin finitus, “limited”) is a verbal action that is not limited by the addition of a subject. In the first sentence, the finite verb “likes” is being attributed to the subject “the boy” – we refer to his action with the verb “likes.” The infinitive “to dance”, “to err”, and “to forgive”, however, simply describe general activities with no presumption of a subject; in other words, an infinitive is not limited by a subject.
In some contexts, the infinitive can be translated with what we would term the gerund form of the verb: “[verb]ing”. This is primarily the case when the infinitive is used with a definite article, as we’ll discuss below. For example:
- We learned the poems by reading.
- The skill of cooking is difficult to master.
Infinitive Formation
There is an infinitive for each of the following tense and voice combinations that we know so far:
- present active (1st pp)
- present middle/passive (1st pp)
- aorist active (3rd pp)
- aorist middle (3rd pp)
- aorist passive (6th pp)
Like their finite counterparts, infinitives are formed from the appropriate principal parts for the tense and voice in question, as indicated in parentheses after each tense-voice combination above.
Present Infinitives
To form a present infinitive, we need to get our present stem as usual from the first principal part and then add an appropriate ending, depending on the voice of the desired infinitive and whether the verb in question is -ω or -μι:
| Present Active | Present Middle/Passive | |
|---|---|---|
| -ω Verbs | -ειν | -εσθαι |
| -μι Verbs | -ναι | -σθαι |
So, the verb κελεύω, with a present stem of κελευ-, would have the present active infinitive κελεύειν (“to order”) and the present middle/passive infinitive κελεύεσθαι (“to order [for oneself]” if middle, “to be ordered” if passive).
The δείκνυμι, on the other hand, would have the present active infinitive δεικνύναι (“to show”) and the present middle/passive infinitive δείκνυσθαι (middle: “to show [for oneself]”; passive: “to be shown”).
Be aware that if the verb in question is an epsilon contract, you will need to contract the ending and the epsilon in the verb stem as usual. So, for example, ποιέω will have a present active infinitive of ποιεῖν (ποιε- + -ειν) and a present middle/passive infinitive of ποιεῖσθαι (ποιε- + -εσθαι).
Core Four -μι Verbs and εἰμί - Present Infinitives
Note that the core four -μι verbs (δίδωμι, τίθημι, ἵημι, ἵστημι) will use their short vowel stems (διδο-, τιθε-, ἱε-, and ἱστα-) in the formation of the present infinitive, both active and middle/passive:
| Present Active | Present Middle/Passive | |
|---|---|---|
| δίδωμι | διδόναι | δίδοσθαι |
| τίθημι | τιθέναι | τίθεσθαι |
| ἵημι | ἱέναι | ἵεσθαι |
| ἵστημι | ἱστάναι | ἵστασθαι |
Also, note that the present active infinitive of the verb εἰμί is εἶναι (“to be”).
Aorist Infinitives and Un-Augmenting
Aorist infinitives are built either off the 3rd principal part (for active and middle infinitives) or the 6th principal part (for passive infinitives). Like their present tense counterparts, the formation of an aorist infinitive is basically the combination of an appropriate stem with an appropriate ending for the desired tense-voice combination.
HOWEVER, there is one extra step that we need to take with aorist infinitives before we add endings to their respective stems. Recall that the 3rd and 6th principal parts of verbs come prepackaged with an augment which indicates that the finite verb form is in a past tense and in the indicative mood. This augment can be either syllabic (ἐ-, as in βλέπω > ἔβλεψα) or temporal (a lengthened initial vowel/diphthong, as in ἀκούω > ἤκουσα).
An infinitive, however, is not a finite indicative verb, and as we’ll learn later, its tense does not necessarily indicate that the verb’s action is happening in the past. So, aorist infinitives should not have augments. As a result, we need to UN-augment the verbal stem in an aorist infinitive.
If the augment is syllabic (ἐ-), this process is simple enough: simply remove the ἐ-. For example, to form the aorist infinitives of the verb βλέπω (3rd pp. ἔβλεψα, 6th pp. ἐβλέφθην), the removal of the syllabic augment results respectively in the stems βλεψ- and βλεφθ-.
If the augment is temporal, however, we can downgrade the vowel to an unlengthened form in one of two ways:
- compare the 3rd/6th principal part against the 1st principal part. The 1st principal part will always begin with an unlengthened form of the vowel/diphthong, and you can change the initial vowel or diphthong of the 3rd or 6th principal part to its counterpart in the 1st. For example: the third principal part of ἀκούω is ἤκουσα, while its 6th is ἠκούσθην. When we compare initial vowels, the α- of the 1st pp has turned into the η- of the 3rd and 6th. So, we can simply reverse the process to create the aorist infinitive stems ἀκουσ- (3rd) and ἀκουσθ- (6th).
- use this textbook’s principal parts list. In this textbook’s verb principal parts list, there will be a stem in parentheses after any 3rd or 6th principal part with a vowel/diphthong downgrade that is not immediately intuitive when we compare those principal parts against the 1st. For example: the third principal part of αἱρέω is εἶλον. In parentheses following εἷλον is the notation “(stem ἑλ-).” This means that any unaugmented verbal forms of the 3rd principal part (including the aorist active and middle infinitives) will be built on the stem ἑλ-. Note some sample verbs for which this is the case: αἱρέω (εἷλον > ἑλ-), ἔρχομαι (ἦλθον > ἐλθ-), λέγω (εἶπον > εἰπ-), and φέρω (ἤνεγκον > ἐνεγκ-).
Once we have removed the augment from the stem, we can attach the appropriate ending to that stem, based on the infinitive’s voice and (if active or middle) whether it is a weak/1st or strong/2nd aorist:
| Aorist Active | Aorist Middle | Aorist Passive | |
|---|---|---|---|
| 1st Aorist | -αι* | -ασθαι* | -ῆναι |
| 2nd Aorist | -εῖν | -έσθαι | -ῆναι |
* In a 1st aorist active or middle infinitive, the accent persists on the last syllable of the stem.
So, note the following aorist infinitives based on the forms used as examples above; first principal parts are listed in the left-hand column:
| Aorist Active | Aorist Middle | Aorist Passive | |
|---|---|---|---|
| βλέπω | βλέψαι | βλέψασθαι | βλεφθῆναι |
| ἀκούω | ἀκοῦσαι | ἀκούσασθαι | ἀκουσθῆναι |
| αἱρέω | ἑλεῖν | ἑλέσθαι | αἱρεθῆναι |
| ἔρχομαι | ἐλθεῖν | ἐλθέσθαι | – |
| λέγω | εἰπεῖν | εἰπέσθαι | – |
| φέρω | ἐνεγκεῖν* | ἐνεγκέσθαι* | ἐνεχθῆναι |
* Note that φέρω also has a rarer 1st aorist form (ἤνεγκα), which would result in the aor. act. inf. ἐνέγκαι and the aor. mid. inf. ἐνέγκασθαι.
Core Four -μι Verbs - Aorist Infinitives
The aorist infinitives of the core four -μι verbs built on the third principal part are more irregular than their present counterparts and should be memorized:
| Aorist Active | Aorist Middle | |
|---|---|---|
| δίδωμι | δοῦναι | δόσθαι |
| τίθημι | θεῖναι | θέσθαι |
| ἵημι | -εἷναι | -ἕσθαι |
The verb ἵστημι’s aorist infinitives will depend on whether you need the transitive or intransitive form:
| Aorist Transitive | Aorist Intransitive | |
|---|---|---|
| ἵστημι | στῆσαι | στῆναι |