Singular

There are four indefinite articles in the singular. These are un (male), uno (male), una (female) and un' (female). The indefinite article (= l'articolo indeterminativo) is used when it is unclear who or what one is talking about. So when talking about an unknown or general person or about an unknown or general matter. If one repeats the person or the thing, then the specific article is used for this.

Un is masculine and comes before nouns that start with a consonant, with a vowel (A, E, I, O, U) or with a mute h kick off. If a noun begins with the vowel i + another vowel, then the indefinite article un is not used.

Uno is also masculine and is used for nouns that start with s + a consonant, with gn, pn, ps, x, y, z or start with i (vowel) + a vowel.

The indefinite article una is feminine and comes before nouns that start with a consonant, with s + a consonant, with gn, pn , ps, x, y, z or start with the vowel i + another vowel.

Un' is feminine and is used when the noun begins with a vowel (A, E, I, O, U) or with a silent h. However, Un' does not precede the vowel i + another vowel.

! IMPORTANT !:
A apostrophe is used for un only for female nouns ➔ un' (un’amica). For masculine nouns no apostrophe is used ➔ un (un amico).