Learn Italian: Dove sono i miei guanti? Li ho lasciati in macchina. - Where are my gloves? I left them in the car.

Normally, when you form the past tense with the helper verb avere (like ho), the past participle ends in -o (ho lasciato). However, when you put a direct object pronoun like lo, la, li, or le before the verb, the past participle has to change its ending to match the pronoun. Since li is masculine plural (replacing the gloves, i guanti), lasciato changes to lasciati.

Why is the pronoun li placed in front of the verb?

In English, we put the object after the verb ("I left them"). In Italian, direct object pronouns like li (them) almost always go immediately before the conjugated verb. Here, the conjugated verb is the helper verb ho, so li must go right in front of it: li ho lasciati.

Why is "in the car" translated as just in macchina instead of nella macchina?

For everyday locations and modes of transportation, Italian often uses the preposition in without combining it with a definite article (the word for "the"). This is why you say in macchina (in the car), in treno (on the train), or in banca (at the bank). You would usually only use nella if you were talking about a specific car, like nella macchina di Paolo (in Paolo's car).