Learn Italian: Questo piatto piccante è preparato da Marco, ma è impossibile da digerire. - This spicy dish is prepared by Marco, but it is impossible to digest.

In Italian, when an adjective describes how a specific noun relates to an action (like being easy, hard, or impossible to do), you connect the adjective to the infinitive verb with da. We use da here because the subject (Questo piatto) is the thing actually receiving the action of the verb (digerire).

The word da appears twice here. Are they doing the same job?

No, they are doing two entirely different jobs! In preparato da Marco, da means 'by' and introduces the person doing the action in a passive sentence. In impossibile da digerire, da is the grammar glue connecting the adjective to the verb, translating to 'to' in 'impossible to digest'.

Why can't I say è impossibile di digerire?

You use di after adjectives only in impersonal structures where there is no specific subject, like È impossibile digerire questo piatto (It is impossible to digest this dish). But when the sentence has a specific subject that the adjective describes (Questo piatto... è impossibile), you must use da before the infinitive.

Is è preparato just a standard past tense?