morior.

From Proto-Italic *moriōr, from Proto-Indo-European *mr̥yétor, from Proto-Indo-European *mer- (“to die”). The oscillation between third and fourth conjugation verbs in this term is comparable to the same variation displayed by other terms with roots ending in -r, such as orior (“to rise, be born”). Moreover, there are some verbs with roots ending in -r that belong to the third conjugation and others to the fourth conjugation, such as the third conjugation term pariō (“to beget”) and the fourth conjugation verb feriō (“to hit”). Weiss tentatively explains this variation as the result of some analogical development, noting that many of these verbs belong to the same semantic field. For instance, morior and orior are antonyms, and pariō can be construed as a causative of orior. Alternatively, Schrivjer interprets this variation is evidence of an original athematic i-present. Cognate with Ancient Greek βροτός (brotós, “mortal”), Proto-Germanic *murþaz, Proto-Celtic *marwos, Lithuanian mirti (“death”), Sanskrit मृत्यु (mṛtyú, “death”), Proto-Slavic *merti. Related to mors (“death”).