The articles

Gli articoli (The articles)

Part I. Gli articoli indeterminativi

Introduction. The indefinite articles are equivalent to English "a," or "an." They are always singular.

In Italian, there are four: un, uno, una, and un'.

un = masculine words starting w/vowel OR cons.
uno = masculine, before z or s plus a consonant.
una = ALL feminine words starting with consonant.
un' = ALL feminine words starting with a vowel.

Part II. Gli articoli determinativi (Definite Articles)

The definite article is equivalent to English "the." Whereas English has only one to be used before all nouns, Italian has several forms, use determined by how the noun begins (consonant, vowel, s + cons.) or by its gender or by whether the noun is singular or plural.

il = masc. singular, before MOST consonants
lo = masc. singular, before s + cons. OR z
l' = masc. or fem. singular, before a vowel
la = fem. singular, before all consonants
i = masc. plural, before MOST consonants
gli = masc. plural, before s + cons.
before z
before all vowels
le = fem. plural, before any cons. or vowel

Part III. Special uses of definite articles with geography.

With place names, Italians apply the above rules to definite article use as much as possible. A place that ends in -o is considered masculine; a place that ends in -a "looks" feminine. Places that end in a consonant are simply considered masculine.

Cities never use an article. Use the preposition "a" to mean "in," "inside of," or "to" a city.

Countries, regions, rivers, mountains most often use the definite article. Exception: after the verb "andare," if these place names are unmodified (no adjective, no qualifying phrase), simply use "in":

in Italia, but nell'Italia centrale
in Francia, but nella Francia meridionale

Part IV. Other special uses of the definite article.

Italian uses the article much more often than English does. It is used when referring to general categories or concepts. Compare:

La pazienza è una virtù. = Patience is a virtue.
Invitiamo gli amici. = We are inviting friends.
Amo i ciocciolatini. = I love chocolates.

When referring to languages, use the adjective of nationality plus the masculine singulare article:

Insegnano l'italiano, il francese, il giapponese, il tedesco, e lo spagnolo all'università.

After the verb "parlare," the article is dropped:

Parli francese? No, ma parlo spagnolo e un po' di tedesco.

Source: The Italian Program at the University of Kentucky