Italian Grammar: ITALIAN DEFINITE ARTICLES

a. Masculine

Il : for masculine singular nouns which start with a consonant.

E.g.: Il libro / the book

L' : for masculine singular nouns which start with a vowel.

E.g. L' orologio / the watch

I : for masculine plural nouns which start with a consonant.

E.g. I libri / the books

Gli : for masculine plural nouns which start with a vowel.

E.g. Gli orologi / the watches

b. Feminine

La : for feminine singular nouns which start with a consonant.

E.g. La penna / the pen

L' : for feminine singular singular nouns which start with a vowel.

E.g. L' ape / the bee

Le : for feminine singular nouns which start with a vowel or a
       consonant.

E.g. Le penne; Le api / the pens; the bees