There are several words in Italian that have two plural forms—a masculine and a feminine. Many of these are related to parts of the body and have diverse meanings.
IRREGULAR PLURALS
SINGULAR
MASCULINE PLURAL
FEMININE PLURAL
braccio
i bracci (arms of a lamp or cross)
le braccia (arms)
budello
i budelli (streets, alleyways)
le budella (intestines)
calcagno
i calcagni (ankles)
stare alle calcagna (to follow someone closely)
ciglio
i cigli (edge, rim)
le ciglia (eyelashes)
dito
i diti (used when followed by the finger’s name)
le dita (fingers)
labbro
i labbri border, brim
le labbra lips
osso
gli ossi (bones for dogs to eat)
le ossa (bones)
There are also body parts with masculine and feminine plurals that have the same meaning. One such example is ginocchio. Both i ginocchio and le ginocchia refer to "the knees."