Breakdown of Potresti cucire la camicia che ho lavato?
avere
to have
potere
can, to be able to
lavare
to wash
la
her/it (direct object)
Questions & Answers about Potresti cucire la camicia che ho lavato?
Why use potresti instead of puoi here?
Potresti is the present conditional form of potere (to be able to), meaning "could you". We use it to make polite requests. Puoi (can you) would also be grammatically correct, but potresti softens the request to sound much more polite, just like in English.
Why doesn't cucire change its ending?
Because it comes right after potresti, which is a modal verb. When a modal verb (verbs expressing wanting, being able to, or having to) is conjugated, the action verb that follows it must stay in its full infinitive form. So, we leave it as cucire (to sew).
Why is it ho lavato instead of ho lavata to match the feminine la camicia?
When forming the past tense (passato prossimo) with the helper verb avere, the past participle (here, lavato) usually doesn't change its ending to match the noun. It stays ending in -o. It would only change to lavata if we used a direct object pronoun right before the verb, like l'ho lavata (I washed it).
In English I could just say "the shirt I washed". Can I drop che in Italian?