Formation of Italian Plural Nouns Ending in -O

Italian singular nouns that end in -o form the plural by changing the ending to -i:

• bambino—bambini
• impiegato—impiegati
• sasso—sassi
• coltello—coltelli

The plural of the noun uomo is also formed with -i, but with a change in the ending: uomini. Of the few female nouns that end in -o, some remain unchanged in the plural; mano usually becomes mani; eco, which in the singular is feminine, is always masculine in the plural: gli echi.

• Nouns in -co and -go do not follow a consistent behavior in forming the plural. If there is a pattern to speak of, the nouns maintain the velar consonants /k/ and /g/, and end in -chi and -ghi. However, if the nouns are sdruccioli (stressed on the third-to-last syllable of a word), instead, drop the velar consonants /k/ and /g/ and add the palatal sounds -ci and -gi:
• baco—bachi
• cuoco—cuochi
• fungo—funghi
• albergo—alberghi
• medico—medici
• sindaco—sindaci
• teologo—teologi
• ornitologo—ornitologi

Among nouns that behave differently from the conventional pattern are:

• nemico—nemici
• amico—amici
• greco—greci
• porco—porci

Among nouns that are pronounced with the stress on the third-to-last syllable, there are many more exceptions:

• carico—carichi
• incarico—incarichi
• abbaco—abbachi
• valico—valichi
• pizzico—pizzichi
• strascico—strascichi
• dialogo—dialoghi
• catalogo—cataloghi
• obbligo—obblighi
• prologo—prologhi
• epilogo—epiloghi
• profugo—profughi

Finally, some nouns have both forms:

• chirurgo—chirugi, chirurghi
• farmaco—farmaci, farmachi
• manico—manici, manichi
• stomaco—stomaci, stomachi
• sarcofago—sarcofagi, sarcofaghi
• intonaco—intonaci, intonachi

Nouns ending in -ìo (with a stressed i) form regular plurals ending in -ìi:

• zìo—zìi
• pendìo—pendìi
• rinvìo—rinvìi
• mormorìo—mormorìi

NOTE: dìo becomes dèi in the plural.

• Nouns ending in -ìo (with an unstressed i) lose the i of the stem in the plural, therefore ending in -i:
• viaggio—viaggi
• figlio—figli
• coccio—cocci
• raggio—raggi
• bacio—baci
• giglio—gigli

NOTE: tempio becomes templi in the plural.

Some nouns that end in -io in the singular, in the plural may be confused with other plurals of the same spelling; to avoid ambiguity are sometimes used, such as an accent on the stressed syllable, a circumflex accent on the ending, or on the final double i:

• osservatorio—osservatori, osservatòri, osservatorî, osservatorii
• osservatore—osservatori, osservatóri
• principio—principi, princìpi, principî, principii
• principe—principi, prìncipi
• arbitrio—arbitri, arbìtri, arbitrî, arbitrii
• arbitro—arbitri, àrbitri
• assassinio—assassini, assassinî, assassinii
• assassino—assassini
• omicidio—omicidi, omicidî, omicidii
• omicida—omicidi

Today the tendency is to write a single i without diacritical marks: the general meaning of the sentence usually resolves any doubt.

Some nouns ending in -o, which in the singular are masculine, in the plural become feminine grammatical gender and take the ending -a:

• il centinaio—le centinaia
• il migliaio—le migliaia
• il miglio—le miglia
• il paio—le paia
• l'uovo—le uova
• il riso (il ridere)—le risa

The table below summarizes the formation of the plural for Italian nouns ending in -o: