Learn Italian: Loro non hanno studiato stamattina. - They didn't study this morning.

In Italian, the past tense (called passato prossimo) is usually made of two parts: a helper verb (like avere, meaning "to have") and the main verb ending in -ato, -uto, or -ito (the past participle). So hanno studiato literally means "they have studied", but it is the standard way to say "they studied" or "they did study" in Italian.

Why does non come before hanno instead of before studiato?

When you make a two-part verb negative in Italian, the non always goes right before the helper verb. You say non hanno studiato, never hanno non studiato.

Is stamattina a single word?

Yes, but it is formed by squishing two words together! It comes from questa mattina (this morning). Over time, Italians shortened it to stamattina, which is now the most common and natural way to say it.

Could I drop loro and just say Non hanno studiato stamattina?

Absolutely! Because hanno already tells us the subject is "they", the word loro is optional. You only need to include it here if you want to add emphasis, like saying "They didn't study this morning (but someone else did)."