(By Hedvig Skirgård): "This question concerns a bound grammatical marker of plural number on nouns. This feature contrasts with GB318 Is plural number regularly marked in the noun phrase by a phonologically free element? which focuses on non-bound marking of plural number. For more on bound marking, please see this page. Bound marking of number on nouns derived from other word classes (such as adjectives or verbs) does not suffice for a 1. Reduplication (full or partial) does not count for this feature. ❡
The marker should occur with an open set of nouns, not with a restricted set. Classes of animate nouns or human nouns are large and open enough. Kinship terms however are a restricted set since it is very hard to add new members. ❡
Number marking is often fused with marking of other categories, such as definiteness/specificity or gender/noun class. It is possible for the number marker to also signal other functions and be coded as 1, as long as these other functions do not interfere with the number distinctions and as long as number marking is productive and regular."