§105. Variable Nouns

Nouns that vary in Declension are called heteroclites. ¹

a. Colus (F.), distaff; domus (F.), house (see § 93), and many names of plants in -us, vary between the Second and Fourth Declensions.

b. Some nouns vary between the Second and Third: as, iūgerum, -ī, -ō, ablative -ō or -e, plural -a, -um, -ibus; Mulciber, genitive -berī and -beris; sequester, genitive -trī and -tris; vās, vāsis, and (old) vāsum, -ī (§ 79. e).

c. Some vary between the Second, Third, and Fourth: as, penus, penum, genitive penī and penoris, ablative penū.

d. Many nouns vary between the First and Fifth (see § 98. c).

e. Some vary between the Third and Fifth. Thus, requiēs has genitive -ētis, dative wanting, accusative -ētem or -em, ablative -ē (once -ēte); famēs, regularly of the third declension, has ablative famē (§ 76. N. 1), and pūbēs (M.) has once dative pūbē (in Plautus).

f. Pecus varies between the Third and Fourth, having pecoris, etc., but also nominative pecū, ablative pecū; plural pecua, genitive pecuum.

g. Many vary between different stems of the same declension: as, femur (N.), genitive -oris, also -inis (as from † femen); iecur (N.), genitive iecinoris, iocinoris, iecoris; mūnus (N.), plural mūnera and mūnia.