The Italian article is chosen by the noun's gender and the sound it starts with: *lo* and *gli* before s+consonant, z, gn, ps, x and y; *il* and *i* before all other consonants; *l'* before a vowel.
All the forms at once
Masculine singular: il libro, lo studente, l'amico. Masculine plural: i libri, gli studenti, gli amici.
Feminine singular: la casa, l'amica. Feminine plural: le case, le amiche — the feminine is the easy half, with no sound-based exceptions.
Indefinite: un libro, uno studente, un'amica, una casa. Mind the apostrophe: un amico is masculine and takes none, un'amica is feminine and takes one.
Why *lo* exists
It isn't arbitrary: lo appears wherever il would make the word awkward to say. Try pronouncing "il studente" and the rule explains itself.
Hence the list: s + consonant (lo sport), z (lo zaino), gn (lo gnocco), ps (lo psicologo), x, y (lo yogurt). In the plural they all become gli.
Where Italian uses an article and English doesn't
Before possessives: it's la mia casa, never mia casa. The exception is singular family members: mia madre, mio fratello — but la mia famiglia.
Before abstract and general nouns: la libertà, il tempo, l'amore. English says "freedom is", Italian says "the freedom is".
Before country names: vado in Italia, but *l'Italia è bella*. It disappears after the preposition and comes back as a subject.
Related questions
When do you use lo instead of il?
Before s+consonant, z, gn, ps, x and y. In every other masculine case it's il, and l' before a vowel.
Is it un'amico or un amico?
*Un amico*, no apostrophe: it's masculine. The apostrophe marks the feminine — *un'amica*.
Updated 2026-07-29