In English, when you witness an action happening, you might use an "-ing" form or a base verb: "I see the juggler smiling" or "I hear the siren sound". In Italian, you express this by pairing a conjugated verb of perception—like vedere (to see) or sentire (to hear)—with an infinitive verb.
The standard sentence structure is: conjugated perception verb + noun/object + infinitive.
| I see the juggler smiling and I hear the passers-by applauding. | Vedo il giocoliere sorridere e sento i passanti applaudire. |
| Suddenly I hear a siren sounding far away. | Improvvisamente sento una sirena suonare lontano. |
Other perception verbs
This exact same structure is used for other verbs related to observing and listening, such as guardare (to watch) and ascoltare (to listen to).
| The passers-by watched the actor perform in the square. | I passanti guardarono l'attore recitare in piazza. |
| The students listened to the musician playing in the square. | Gli studenti ascoltarono il musicista suonare in piazza. |
Using different tenses
The perception verb can be conjugated in any tense (like the past tense) or follow a modal verb like volere (to want). Regardless of how the main verb changes, the action you are observing always stays in the infinitive.
| Last night I saw Marco playing the guitar and the violin. | Ieri sera ho visto Marco suonare la chitarra e il violino. |
| I would like to hear the musician sing without playing the guitar. | Vorrei sentire il musicista cantare senza suonare la chitarra. |
Infinitive before the object
While the object usually sits between the two verbs, you can also place the infinitive directly after the perception verb, putting the noun at the end. This is especially common when the noun phrase is long, or when you are listing multiple things.
| I hear the violin and the drum playing, and I hear the applause. | Sento suonare il violino e il tamburo, e sento l'applauso. |