5.4.1. Inanimate nouns in Arapaho regularly distinguish between singular and plural forms. The absolute form of an inanimate noun is the uninflected singular form. According to the formal marking of the plural (morpheme 221), the class of inanimate nouns may be divided into two subclasses, each of which subdivides further. Following the procedure established in 5.3, the sorting of the inanimate nouns stops short of detailing prosodemic differences. 5.4.2.1. Subclass I of the inanimate nouns comprises those stems which form their plural by suffixing morpheme 221 in the shape of -o. Four divisions of this subclass are recognized; they consist of sets defined and exemplified below. 5.4.2.1.1. Nouns assigned to Division 1 add the suffix -o to the absolute form of their stems, which are terminated in -Vn. Examples are: b6Oen breast, b6Oeno (15, N, 221/b-6een-o); hiik6n N hiikon lung, hiik6no N hiikono (N, 221 / hiik6n hiikon-o); b6sonon ' b6son6n neck, b6son6no (15, N, 221 /b-6son6n-o); niyiinon tepee, niyiin6no (N, 221 / niyiin6n-o); and beiO6n tongue, beiO6no (15, N, 221/bei06n-o). 5.4.2.1.2. Nouns assigned to Division 2 re-