IL PLURALE

1) 

il pino   i pini

Generally,  the plural form of masculine words ending in "-o" is obtained by replacing the final "-o" with "-i". However, this group includes some invariable words and some irregular nouns.

2)  

la torta le torte

Generally,  the plural form of feminine words ending in "-o" is obtained by replacing the final "-o" with  "-e". 

   Exceptions: ala (wing) ali    arma (weapon) armi    frutta (fruit) frutta

3) 

il ponte i ponti
la mente le menti

Normally, the plural form of masculine and feminine words ending in  "-e" ends in "-i".

4)

il/la barista i baristi, le bariste
il/la matricida i matricidi, le matricide  

Some singular nouns ending in "-ista" and "-cida" can refer to both men and women (please note that the article changes according to gender). Masculine nouns in this group end in "-i", feminine nouns end in "-e".

5) 

il baco i bachi
la foca le foche
il lago i laghi
la lega le leghe

Masculine and feminine words ending in "-co/ca" or "-go/ga" and stressed on the next-to-the-last syllable usually add an "h" before the plural ending, in order to retain the hard soung /k/ and /g/. 

    Exceptions :

porco   

pig   

porci    

pigs
amico friend amici friends
nemico foe nemici foes
greco Greek greci greeks
procio*(arcaico) Penelope pursuer proci  

    6) la monaca --> le monache      la psicologa --> le psicologhe
Feminine words ending in "-ca" or "-ga" and stressed on the next-to-the-last syllable add an "h" before the plural ending, in order to retain the hard soung /k/ and /g/. 

    7)  il medico --> i medici                 lo psicologo --> gli psicologi    
Masculine words ending in "-co" e "-go" and stressed on the second-to-the-last syllable do not retain the hard sound /k/ and /g/ in the plural, and therefore use the "-ci/gi" ending.

    Exceptions:  

àbaco  

abacus  

abachi  

abaci

apòlogo

apologue

apologhi

càrico

load

carichi

loads

catàlogo

catalog

cataloghi

catalogues

decàlogo

decalogue

decaloghi

diàlogo

dialogue

dialoghi

dialogues

epìlogo

epilog 

epìloghi

 

incàrico

assignment

incarichi

 

intònaco

plaster 

intonaci

 

monòlogo

monologue 

monòloghi

monologues

òbbligo

obligation

òbblighi

 obligations

pèlago

sea

pèlaghi

 

pìzzico

pinch

pizzichi

 

pròlogo

prologue

pròloghi

 

rammàrico

regret

rammarichi

 

sàrago

white bream 

sàraghi

 

scàrico

unloading 

scarichi

 

sollètico

tickle

solletichi

 

stòmaco

stomach

stomachi

 

stràscico

trailing 

strascichi

 

vàlico

mountain pass

valichi

 

8) 

il brulichìo i brulichìi
l'oblìo gli oblìi
lo zìo gli zii

Masculin nouns ending in "-ìo" (word stress on "i"), retain that stressed "ì" when adding the plural ending; therefore, the plural form ends in "-ìi".

    Exception:   dio --> dei   (god/gods)

8) 

bacio baci
occhio  occhi

Nouns ending in "i" without an accent have only one "i". 

See also the list of of different nouns (e.g., (assassino, assassinio) that share the same plural form a>(assassinio, assassini).

9)

audacia  audacie  
farmacìa  farmacìe

Feminine nouns ending in "-ia" retain the "i" in the plural form even whether it is stressed or not.

10)

caccia  cacce 
boccia  bocce

Feminine nouns with the "-cia" ending preceded by a consonant lose the "i" in the plural. 

    Exceptions: See

Plural Form of Feminine Words Ending in - CIA and -GIA 

Nomi invariabili
Nomi con due plurali
Nomi usati solo al plurale
Nomi maschili al singolare e femminili al plurale
Nomi composti 

Plurali con doppia "i" o diversi per la pronuncia