Here we look at the variable occurrence of nominal plural forms (as in WALS feature 34, by Martin Haspelmath). Some languages plurals entirely, but those languages that have plural forms often use them optionally, or under certain conditions (such as animacy and definiteness). Especially human nouns tend to show plural marking when plural marking is not invariant in the language. Languages with the second value have optional plural marking but restrict it to human nouns. Languages with the third value have optional plural marking of all nouns. Finally, some languages are like the European lexifiers in requiring invariant plural marking.
