Learn Italian: Oggi Marco sta peggio e sta a casa. - Marco is worse today and stays at home.

In Italian, we use the verb stare (to stay/to be) to talk about health and how someone is feeling, rather than essere (to be). Since Marco is feeling worse, we use sta together with the adverb peggio (worse).

In this sentence, sta appears twice. Does it mean the exact same thing both times?

Not quite! The verb stare is very flexible. In the first part (sta peggio), it acts like "is doing" or "feels" (referring to his health). In the second part (sta a casa), it takes its more literal meaning: "stays" or "remains" (at home).

Why is it a casa instead of alla casa?

Stare a casa (to stay at home) is a fixed expression in Italian. When talking about being at, going to, or staying at your own home, you simply use the preposition a without adding the word for "the".

Is stare a regular verb?

No, stare is irregular, which means it doesn't follow the normal pattern for verbs ending in -are. While Marco (he) is sta, "I stay" is io sto and "they stay" is loro stanno.