Il gerundio e il participio
The gerundio is Italian's all-purpose '-ing' adverbial: it expresses HOW, WHILE, BY, or BECAUSE another action is done. Form: -are → -ando, -ere / -ire → -endo: parlando, leggendo, dormendo. The gerundio composto = avendo or essendo + past participle, marking an action that happened BEFORE the main verb. With stare as auxiliary, the gerundio builds the progressive: sto parlando = I'm (in the act of) speaking. The participio passato has its own life as an adjective AND in compact subordinate clauses: finito il lavoro, sono uscito = (the) work finished, I went out.
Gerundio semplice: forming -ando / -endo
-are verbs → -ando: parlare → parlando, mangiare → mangiando, studiare → studiando. -ere and -ire verbs → -endo: leggere → leggendo, vivere → vivendo, dormire → dormendo, partire → partendo. A few irregular forms keep their original Latin stem: fare → facendo, dire → dicendo, bere → bevendo, porre → ponendo, tradurre → traducendo. The gerundio is INVARIABLE — no agreement with subject. Pronouns attach to the end: vedendolo = seeing it, parlandogli = speaking to him, alzandosi = getting up.
What the gerundio does: simultaneity, manner, cause, condition
Four jobs, all 'while / by / because / if -ing' in English. SIMULTANEITY: Camminando, pensavo a te. = Walking, I was thinking about you. MANNER: Si è ferito cadendo. = He hurt himself falling. CAUSE: Essendo stanco, sono andato a letto. = Being tired, I went to bed. CONDITION: Studiando di più, passerai l'esame. = (By) studying more, you'll pass the exam. Crucially, the SUBJECT of the gerundio must be the same as the subject of the main verb: Camminando has the same 'I' as pensavo. With a different subject, you need a full subordinate clause (Mentre camminavo, Marco parlava. — NOT Camminando, Marco parlava if it's two different people).
Gerundio composto: avendo / essendo + participle
When the gerundio action happened BEFORE the main verb, use the compound: avendo (or essendo for essere-verbs) + past participle. Avendo finito il lavoro, sono uscito. = Having finished the work, I went out. Essendo arrivato presto, ho aspettato fuori. = Having arrived early, I waited outside. Avendo letto il libro, sapevo già la fine. = Having read the book, I already knew the ending. With essere-verbs, the participle agrees with the (implied) subject: essendo arrivata if 'I' is feminine. Pronouns attach to avendo / essendo: avendolo visto = having seen him.
Stare + gerundio: the progressive
stare + gerundio = the English '-ing' progressive (action in progress RIGHT NOW or AT THE MOMENT in question). Present: sto parlando = I'm speaking. Imperfetto: stavo parlando = I was speaking. Sto leggendo un libro. = I'm reading a book. Stavamo cenando quando hai chiamato. = We were having dinner when you called. Italian uses the progressive LESS than English — the simple presente often does the job: leggo can mean both 'I read' and 'I'm reading'. Use stare + gerundio when you specifically want to emphasize the action is ONGOING right at this moment. It can't be used for future plans: sto andando domani is wrong; say vado domani.
Participio passato as a compact subordinate
The past participle alone (without an auxiliary) can introduce a compact temporal/causal clause meaning 'once X-ed' / 'after X-ing'. The participle agrees in gender and number with the noun it refers to. Finito il lavoro, sono uscito. = (Once) the work was finished, I went out. Letto il libro, l'ho restituito. = Having read the book, I returned it. Arrivata Anna, abbiamo iniziato. = Once Anna arrived, we started. Una volta + participle is a fixed phrase: una volta finito = once finished, una volta arrivati = once arrived. This construction is COMMON in writing and journalism, terser than the gerundio composto, with the same anteriority meaning.
