2. Singular and plural
In addition to inflecting in terms of gender, nouns can usually also be inflected in number. When forming the plural, nouns can be categorized into three groups according to the ending of the noun in singular.
| Group I – nouns ending in -o in singular | |
| Singular | Plural |
| -o | -i (regardless of gender) |
| il libro | i libri |
| l’albero | gli alberi |
| la mano | le mani |
i libri
| Group II – nouns ending in -a in singular | |
| Singular | Plural |
| -a | -e (if the word is feminine) |
| la casa | le case |
| la mela | le mele |
| Singular | Plural |
| -a | -i (if the word is masculine) |
| il problema | i problemi |
| il poeta | i poeti |
le mele
| Group III – nouns ending in -e in singular | |
| Singular | Plural |
| -e | -i (regardless of gender) |
| il cane | i cani |
| il padre | i padri |
| la madre | le madri |
i cani
There are also nouns that have the same form in both singular and plural and that cannot be inflected. The gender can be determined by looking at the article.
These include monosyllabic words (il re king ⇒ i re), words that end in an accented vowel (il caffè coffee ⇒ i caffè), some masculine nouns that end in -a (il cinema movie theatre ⇒ i cinema) as well as masculine nouns that end in a consonant (il computer computer ⇒ i computer).
These also include feminine nouns that cannot be inflected and that end in -o (la radio radio ⇒ le radio), -ie (la serie series ⇒ le serie) and -i (l’analisi analysis ⇒ le analisi).
There are also nouns that either have only the singular form (so-called uncountable nouns) or only the plural.
EXAMPLES:
l’acqua water (only singular)
gli occhiali glasses (only plural)
Finally, there are a few nouns that have two different plural forms. The plural forms have different meanings.
EXAMPLE:
il muro wall
i muri (e.g. of a house)
le mura (e.g. of a city)