There are also a number of nouns which do not end in "-o" or "-a."
Nouns ending in "-e," whether masculine or feminine, invariably form the plural in "-i":
"il fiore" <the flower>, "I fiori" <the flowers>;
"la lezione" <the lesson>; "le lezioni"<the lessons>.
Nouns ending in "-i" or an accented vowel do not change in the plural:
"la crisi" <the crisis>, "le crisi" <the crises>;
"la virtù" <the virtue>, "le virtù" <the virtues>;
"la città" <the city>, "le città" <the cities>.
The same is true of one-syllable nouns, and of foreign loanwords ending in a consonant:
"il re" <the king>, "i re" <the kings>;
"il film" <the movie>, "i film" <the movies>.
Some nouns ending in "-a" or "-e" can be either masculine or feminine, depending on the gender of the person being named by the noun:
"il pianista" <the male pianist>; "la pianista" <the female pianist>;
"il cantante" <the male singer>, "la cantante" <the female singer>.
Other nouns change their ending according to gender:
"l'attore" <the actor>, "l'attrice" <the actress>;
"il gallo" <the rooster>, "la gallina" <the hen>;
"il cameriere" <the waiter>, "la cameriera" <the waitress>.
There are also nouns that have both genders, but with a different meaning for each:
"il fine" <the purpose>, "la fine" <the conclusion>;
"il tema" <the topic>, "la tema" <fear>.