Noun class in Rau coexists with gender. There are nine noun classes, each of which has two forms; additionally, certain prefixes (those consisting of voiced plosives or |l̠|, or the first form class 1 prefix) have nasal alternants.

Noun classes are prefixed to verbs, as well as third-person pronouns, demonstratives, etc. The form is governed by TODO; the alternant is strictly lexically conditioned.

1P) First person singular
|g- t- ŋ- t-|

2P) Second person singular
|r̠- ƛ- r̠- ƛ-|

PL) Non-third-person plural
|b- y- m- y-|

1) Humans
|y- k- n- k-|

2) Body parts, components, some animates
|d- g- n- ŋ-|

3) Pottery, containers, tools, certain abstracta, most verbal nouns
|l̠- y- n- y-|

4) Collectives
|b- b- m- m-|

5) Land and sky, geographic features
|n- n- n- n-|

6) Abstracta
|š- c- š- c-|

7) Vegetables, nuts, some hard objects
|b- b- m- m-|

8) Liquids, certain abstracta
|c- λ- c- n-|

9) Weapons
|λ- λ- n- n-|