Learn Italian: È una casa.

In Italian, the word for "a" or "an" changes depending on the gender of the noun. We use una because casa (house) is a feminine noun. If the noun were masculine, we would use un.

How can I tell that casa is a feminine noun?

A great rule of thumb for beginners is to look at the ending of the word. Most Italian nouns that end in -a are feminine. Since casa ends in -a, it takes the feminine article una.

Where is the word for "It" in this sentence?

Italian usually drops subject pronouns (like I, you, he, she, or it) because the verb already shows what you are talking about. The word È literally means "is", but on its own, it translates to "It is", "He is", or "She is" depending on the context.

Why does È have an accent mark?

The accent mark changes the meaning of the word. With the accent, è is a verb meaning "is". Without the accent, e simply means "and".