Italian nouns are either masculine or feminine.
As a general rule (with a few exceptions), male human beings are associated to masculine nouns; female human beings are associated to feminine nouns. Collective nouns, referring to a group of human beings of both genders, are usually masculine.
Attore (actor) is masculine. (è maschile) Attrice (actress) is feminine. (è femminile) Maestro (male teacher) is masculine. Maestra (female teacher) is feminine. Bambini (children, a group of little boys) is masculine Bambini (children, a mixed group of little boys and girls) is masculine Bambine (children, a group of little girls) is feminine
Persona (person - man or woman) is feminine
Animals and things may be masculine or feminine, but there is no clear rule for this association. When you learn a new word, you should learn whether it is masculine or feminine.
Pietra (stone) is feminine. Sasso (also stone) is masculine. Topo (mouse) is masculine. Volpe (fox) is feminine.
The basic rule is that masculine singular nouns end with -o, feminine singular nouns end with -a. Most words follow this form, but this is not always the case.
- Masculine singular nouns can end in -a (rare)
- Feminine singular nouns can end in -o (rare)
- Both masculine and feminine nouns can end with -e
- Nouns ending in -à are always feminine
- Nouns ending in -è are always masculine
- Nouns ending in -i and in -ù are usually feminine
- Nouns ending in -ione are always feminine
- Nouns ending in -mma are usually Greek in origin and masculine
Uomo (man) is masculine. Donna (woman) is feminine. Mano (hand) is feminine. Programma (program) is masculine. Cane (dog) is masculine. Pace (peace) is feminine. Città (town) is feminine. Crisi (crisis) is feminine. Virtù (virtue) is feminine.
In Italian, nouns are pluralized by a change in the last vowel.
- Nouns ending with -a are pluralized with -e if feminine (most common) or with -i if masculine.
- Nouns ending with -e or -o are pluralized with -i.
- Nouns ending with a stressed vowel, with -i or -u or with a consonant are invariant, the plural is the same as the singular.
- Feminine in -a, plural in -e
- Feminine in -e, plural in -i
- Feminine in -o, plural in -i
- Feminine in -ie, plural in -ie
- Feminine in -i, plural also in -i
- Masculine in -a, plural in -i
- Masculine in -o, plural in -i (rarely, plural in -a; see Special Plurals below)
- Masculine in -e, plural in -i
A basic example:
[Il] ragazzo (boy) is masculine singular. - [I] ragazzi is the plural form. [La] ragazza (girl) is feminine singular. - [Le] ragazze is the plural form.
[Il] programma (program, masculine). Plural: [i] programmi. [La] mano (hand, feminine). Plural: [le] mani. [Il] cane (dog, masculine). Plural: [i] cani. [La] canzone (song, feminine). Plural: [le] canzoni. [La] crisi (crisis, feminine). Plural: [le] crisi. [La] città (town, feminine). Plural: [le] città. [Il] caffè (coffee, masculine). Plural: [i] caffè. [La] virtù (virtue, feminine). Plural: [le] virtù. [Il] gas (gas). Plural: [i] gas.
In some cases, plural feminine forms can be mistaken for singular masculine forms.
Example of confusing forms.
[Il] signore (mister) is masculine singular. - [I] signori is the plural form. [La] signora (mrs) is feminine singular. - [Le] signore is the plural form.
The problem here is that "signore" can refer to both one man or two (or more) women. This problem is usually solved by taking the article into account.
Special plurals 
A number of masculine nouns ending in -o have special plurals ending in -a; these special plurals switch to feminine gender. They are a remnant of the old Latin neutral gender.
Examples of plurals in -a:
[Il] braccio (arm, masculine). Plural: [le] braccia (feminine) [L'] uovo (egg, masculine). Plural: [le] uova (feminine)
Very few nouns have irregular plurals.
Irregular plurals (example):
Uomo (man), plural: uomini
Some nouns are invariant (the plural is the same as the singular) even if they end in -a, -e or -o. These nouns are usually originated by a shortening of longer names.
Invariant plurals i -a, -e or -o (example):
[La] moto (short for motocicletta) (motorcycle). Plural: [le] moto
Nouns ending with i+vowel in some cases miss one i in the plural (a rule for masculine nouns).
Examples of plurals for nouns in -ia, -io:
Camicia (shirt, fem.). Plural: camicie Doccia (shower, fem.). Plural: docce Arancia (orange, fem.). Plural: arance Inizio (start, masc.). Plural: inizi Negozio (shop, masc.). Plural: negozi Raggio (ray, masc.). Plural: raggi
Nouns ending with -co, -go can have plurals ending with -chi, -ghi or -ci, -gi. Nouns ending with -ca, -ga usually have plurals ending with -che, -ghe.
Examples of plurals for nouns in -co, -go, -ca, -ga:
Amico (friend, masc.). Plural: amici Arco (arch, masc.). Plural: archi Lago (lake, masc.). Plural: laghi Medico (physician, masc.). Plural: medici Amica (friend, fem.). Plural: amiche Barca (boat, fem.). Plural: barche Targa (plate, fem.). Plural: targhe
Particular cases -cia and -gia
Words ending with either -cia and -gia respect the following rule.
Plural ends with -cie/-gie if the final letter before the suffix(cia/gia) is a vowel Plural ends with -ce/-ge if the final letter before the suffix is a consonant
If the stress falls on the i, the i always remains so, for instance, -cia makes the plural with -cie.