Learn Italian: Le mele rosse sono buone. - The red apples are good.

Because we are talking about more than one apple! As taught in this lesson, feminine singular nouns ending in -a (like mela) change their ending to -e to become plural (mele). To match this, the feminine singular article la ('the') changes to the plural article le.

Why do the words for 'red' and 'good' end in -e (rosse, buone)?

In Italian, adjectives must match the noun they describe. Since mele is a feminine plural noun, the base adjectives rosso (red) and buono (good) change their endings to -e to perfectly match the noun they describe.

Wait, doesn't sono mean 'I am'?

It does! But the verb essere (to be) is special: it uses the exact same word, sono, for both 'I am' (io sono) and 'they are' (loro sono). Since 'the apples' acts as a 'they', we use sono here to mean 'are'.

Why is it le mele rosse and not le rosse mele?

In English, we put the describing word before the noun ('red apples'). In Italian, adjectives (especially colors) usually come directly after the noun they describe. So, you literally say 'the apples red'.