Lexical usage

Verbs of saying

ἀρνέομαι ‘to deny’, ἐπαγγέλλομαι, ὑπισχνέομαι ‘to promise’, λέγω ‘to say’, μαρτυρέω ‘to testify’, ὄμνυμι ‘to swear’, ὁμολογέω, συγχωρέω ‘to admit’, φάσκω, φημί ‘to claim’ etc.

Verbs of supposing

δοκέω, ἡγέομαι, νομίζω, οἴομαι ‘to deem, find’, εἰκάζω ‘to guess’, ἐλπίζω ‘to hope, expect’, κρίνω ‘to judge’, πέπεισμαι ‘to be convinced’, πιστεύω ‘to trust’, προσδοκάω ‘to expect’, ὑποπτεύω ‘to suspect’ etc.

Syntactic usage

Subject in case of coreference

When the subject of the main verb and that of the infinitive are identical, the infinitive is used on its own; when the subjects differ, the subject of the infinitive is put in the accusative case (accusativus cum infinitivo).

The expression of temporality

Since it stands in the place of the indicative in direct speech, this infinitive expresses time. This means that the aorist infinitive always refers to the past. The future infinitive only occurs as a declarative infinitive and never as a dynamic infinitive.

The particle ἄν

The particle ἄν can stand with the declarative infinitive, in contrast to the dynamic infinitive (since the latter is deontic). The context must decide whether the intended modality is possibility or counterfactuality, since due to the use of the infinitive in indirect speech it is formally impossible to tell whether an optative or a secondary indicative was used in direct speech.

The negation: usually οὐ

As a rule the negation is οὐ, although μή sometimes replaces οὐ if the main verb implies a wish or expresses determination. This is the case, for instance, after an imperative (e.g. νόμιζε μηδὲν βέβαιον εἶναι ‘Assume that nothing is stable.’).

Varia

The use of tenses and moods

When the main verb is in the aorist the infinitive has the tendency to take the aorist too. This tendency is reversed if the main verb is in the optative. A main verb in the perfect is usually followed by a present infinitive.