Adjectives of three terminations have different endings for each gender, but only in the nominative. The nominative masculine forms take their endings in "er" (cf. noster). The nominative feminine forms of the adjectives will end either 'ris' or 'eris' depending on the stem: e.g. (NS)

äcer audïtor - keen listener; celer audïtor - swift listener

äcris mëns - keen mind; celeris mëns - swift mind

GS - äcris audïtöris - of the keen listener; äcris mentis - of the keen mind

DS - äcrï audïtörï - to the keen listner; äcrï mentï - to the keen mind

AccS - äcrem audïtörem; äcrem mentem

AblS - äcrï audïtöre; äcrï mente