(By Matthew S. Dryer): "This map shows the method by which a language indicates plurality with nouns. There are basically two ways in which languages indicate plurality. The first (and most common) involves changing the morphological form of the noun, as in English dog, dogs. The second involves indicating plurality by means of a morpheme that occurs somewhere else in the noun phrase, illustrated by the plural word in the example in (1) from Hawaiian, where the word mau has the same function as the plural suffix in English, but is a separate word modifying the noun."
Plural words are apparently always bound forms, and can thus be regarded as plural clitics.