Gli alberi circondano il giardino.

The trees surround the garden.

Breakdown of Gli alberi circondano il giardino.

• l'albero: the tree
• il giardino: the garden
• circondare: to surround

Questions & Answers about Gli alberi circondano il giardino.

Why is gli used before alberi instead of i?

In Italian the regular masculine plural article is i, but before a vowel (and certain consonant clusters) it changes to gli. Since alberi begins with the vowel a, the correct definite article is gli, giving gli alberi.

What tense and person is circondano, and how does it match gli alberi?

Circondano is the third-person plural present-indicative form of the verb circondare (to surround). It ends in -ano because its subject, gli alberi, is plural. The full present-tense paradigm is:
io circondo, tu circondi, egli circonda, noi circondiamo, voi circondate, essi circondano.

Why is il used before giardino and not another article?

Giardino is a masculine singular noun ending in -o, and masculine singular nouns beginning with a consonant take the definite article il. Therefore we say il giardino (“the garden”).

How would you express this sentence in the passive voice?

To form the passive, use essere + past participle + agent with da + article.
Active: Gli alberi circondano il giardino.
Passive: Il giardino è circondato dagli alberi.
Note that da + gli contracts to dagli.

Can il giardino be replaced with a pronoun, and if so, which one?

Yes. Since il giardino is masculine singular, its direct-object pronoun is lo. You can say:
 Gli alberi lo circondano.
(“The trees surround it.”)

Is there another way to say “the trees surround the garden” without using circondare?

Yes. You can use the locative phrase intorno a:
 Gli alberi stanno intorno al giardino.
This literally means “The trees are around the garden,” emphasizing position rather than the action of surrounding.