Third Conjugation Verbs

Third Conjugation Verbs
–ire Verbs in Italian

The infinitives of all regular verbs in Italian end in –are, –ere, or –ire and are referred to as first, second, or third conjugation verbs, respectively. In English the infinitive (l'infinito) consists of to + verb.

amare to love

temere to fear

sentire to hear

Verbs with infinitives ending in –ire are called third conjugation, or –ire, verbs. The present tense of a regular –ire verb is formed by dropping the infinitive ending –ire and adding the appropriate endings to the resulting stem. There is a different ending for each person.

Characteristics of the Third Conjugation
# Many –ire verbs add, between the root and declination, the suffix isc to the first, second, and third person singular and third person plural of the indicative and subjunctive present tense, and to the second and third person singular and third person plural of the present infinitive tense:

finire
io finisco che io finisca
tu finisci che tu finisca
egli finisce che egli finisca
essi finiscono che essi finiscano
finisci finisca finiscono

# some verbs have both forms, similar to the model of sentire and finire:
languire io languo io languisco
mentire io mento io mentisco

# other verbs also have both forms but take on diverse significance:
ripartire
io riparto (to leave again)
io ripartisco (to divide)

# Generally the present participle (il participio presente) of third conjugation verbs end in ente, several have the form iente, and a few can have both endings:
morire morente
esordire esordiente
dormire dormente/dormiente
# Some participles change the letter t that precedes the declination of the participle iente to the letter z:
sentire senziente

Source