Learn Italian: Abbiamo usato queste abilità fino a ieri. - We used these skills until yesterday.

Nouns that end in an accented vowel, like abilità (skill), are invariable. This means they have the exact same form in both the singular and the plural. We know it is plural here because the adjective describing it, queste (these), is in the feminine plural form.

If queste abilità is feminine plural, why is the past participle usato and not usate?

When you form the past tense with the helping verb avere (like abbiamo here), the past participle (usato) does not change to match the object that comes after it. It stays in the default masculine singular form ending in -o.

Why do we need the a in fino a ieri? Can we just say fino ieri?

The word fino (until) almost always requires the preposition a to connect it to the next word. When talking about a point in time, you should treat fino a as a fixed pair, like in fino a ieri (until yesterday) or fino a domani (until tomorrow).

Is abilità the best word to use for a learned skill?

Yes! While it is a direct cognate for the English word ability and can translate to that, abilità is also the standard everyday Italian noun for a skill.