The infinitive can be used after certain prepositions, such as per, prima di and senza; whereas in English, the gerund form is usually used.

Siamo pronto per uscire.  We are ready to go out.
Prima di partire.  Before leaving.
Senza dire niente.  Without saying anything.

The past infinitive may be used after senza and dopo.  It is formed with the auxiliaries essere or avere and the past participle of the verb.  The final -e of the auxiliary verb is commonly dropped.

Sono venuti senza aver telefonato.  They came without having telephoned.
È ritornata dopo aver comprato i biglietti.  She returned after having bought the tickets.

The infinitive may also function as a noun.  In this case, the English translation is also the gerund form.

Viaggiare stanca.  Travelling is tiring.

Letting, seeing or hearing someone do something is expressed by the forms of lasciare, vedere and sentire plus the infinitive.

Ho sentito cantare Teresa.  I heard Teresa sing.
Ho veduto dormire i bambini.  I saw the children sleep.

The Subjunctive mood expresses doubt, uncertainty, hope, fear, possibility, opinions, etc. and is used much more frequently in Italian.  It is mainly used in dependent clauses (sentences introduced by a conjunction that do not have a complete meaning) that are introduced by che.

The present subjunctive of regular verbs is formed by dropping the normal endings, and adding these new endings:

Verbs ending in -care and -gare add an h before all endings of the present subjunctive.  Verbs ending in -ciare and -giare drop the i from their stems.

Many common verbs have irregular present subjunctive forms:

The present perfect subjunctive is formed with the present subjunctive of avere or essere and the past participle of the main verb.