Learn Hardcore Italian: Il terzo albero in giardino è vecchio.

In Italian all ordinal numbers used as adjectives normally require the definite article and must agree with the noun. So you say il terzo albero, not just terzo albero.

Why is terzo placed before the noun rather than after it?

Ordinal numbers in Italian function like other descriptive adjectives and go before the noun. Placing it after (e.g. albero terzo) sounds ungrammatical in standard usage.

Why do we use in giardino rather than nel giardino?

When referring to being inside a place in a general sense, Italian often uses in without an article for locations such as in giardino, in casa, in ufficio.
Using nel giardino (“in the garden” with article) is grammatically correct but emphasizes the boundaries of that specific garden and is less common in everyday speech.

Why does the adjective vecchio come after albero, and how does its form change?

• Most Italian adjectives follow the noun they modify.
• Vecchio agrees in gender and number with albero (a masculine singular noun), so it remains vecchio (not vecchia, vecchi, etc.).

How are ordinal numbers like terzo formed in Italian?

• From 4th onward they’re regular: replace the final vowel of the cardinal with –esimo (quarto, quinto, sesto…).
• The first three are irregular: primo, secondo, terzo.
• They agree with the noun’s gender/number: terzo (m. sg), terza (f. sg), terzi (m. pl), terze (f. pl).

Can you omit the article il in this sentence?

No. In normal conversation and writing the article is mandatory with ordinals (il primo, il secondo, il terzo). Omitting it (terzo albero) would sound like a headline or note rather than a complete sentence.

Could you rephrase it as Il terzo albero del giardino è vecchio?

Yes.
• del giardino (“of the garden”) highlights possession.
• in giardino focuses on location.
Both versions are correct but carry slightly different nuances.