Three things decide the article
English has one definite article: the. Italian has several, because the article agrees with the word that follows it: its gender (masculine or feminine), its number (singular or plural) and its first sound. The forms follow a clear logic: il and i are the default, and lo and gli appear where il and i would be hard to pronounce.
The forms at a glance
| Singular | Plural | First sound |
|---|---|---|
| il | i | consonant (default) |
| lo | gli | s + consonant, z, gn, ps |
| l' | gli | vowel |
| la | le | consonant |
| l' | le | vowel |
Singular and plural in pairs
il libro → i libri
the book → the books
lo studente → gli studenti
the student → the students
l'amico → gli amici
the friend → the friends
la casa → le case
the house → the houses
l'amica → le amiche
the (female) friend → the (female) friends
Before a vowel, masculine and feminine look the same in the singular (l'amico, l'amica). The gender only shows in the plural: gli amici, le amiche.
All the forms in sentences
La ragazza legge il libro.
The girl reads the book.
Lo zaino è pesante.
The backpack is heavy.
L'arancia è dolce.
The orange is sweet.
Le chiavi sono sul tavolo.
The keys are on the table.
Gli studenti studiano insieme.
The students study together.
