Geographical distribution[edit]
Obligatory plural marking of all nouns is found throughout western and northern Eurasia and in most parts of Africa. The rest of the world presents a heterogeneous picture. Optional plural marking is particularly common in Southeast and East Asia and Australian languages, and complete lack of plural marking is particularly found in New Guinea and Australian languages. In addition to the areal correlations, there also seems to be at least one correlation with morphological typology: isolating languages appear to favor no or non-obligatory plural marking. This can be seen particularly in Africa, where optionality or absence of plural marking is found particularly in the isolating languages of West Africa.[5][6]
Semantic versus grammatical number[edit]
All languages are able to specify the quantity of referents. They may do so by lexical means with words such as English a few, some, one, two, five hundred. However, not every language has a grammatical category of number. Grammatical number is expressed by morphological or syntactic means. That is, it is indicated by certain grammatical elements, such as through affixes or number words. Grammatical number may be thought of as the indication of semantic number through grammar.
Languages that express quantity only by lexical means lack a grammatical category of number. For instance, in Khmer, neither nouns nor verbs carry any grammatical information concerning number: such information can only be conveyed by lexical items such as khlah 'some', pii-bey 'a few', and so on.[325]