The value plural applies to common and proper nouns. The criterion is a morphosyntactic one and not a semantic one.
numb=pl | |||
D e s c r i p t i o n | E x a m p l e s | ||
Common nouns | le monete/pl | ||
gli studenti/pl | |||
i dollari/pl | |||
Proper nouns | gli Appennini/pl | ||
le due Americhe/pl |