Learn Italian: Preferisco il terzo vestito, non il primo. - I prefer the third dress, not the first.

In Italian, ordinal numbers like terzo (third) and primo (first) usually go before the noun, just like in English. This is different from most descriptive adjectives, which usually go after the noun.

Do ordinal numbers change their endings like other adjectives?

Yes! Ordinal numbers act just like regular adjectives. Because vestito is masculine and singular, we use the -o ending for terzo and primo. If we were talking about a feminine noun like gonna (skirt), they would change to terza and prima.

Why does the sentence just say il primo instead of il primo vestito at the end?

Just like in English, you do not need to repeat the noun if it is already clear from the context. Here, il primo means the first one. Notice that you still need to keep the article il before the ordinal number!

Why is the verb preferisco instead of prefero?

The verb preferire (to prefer) belongs to a special group of -ire verbs that insert the letters -isc- into the stem for most present tense forms. This is why I prefer translates to preferisco.