§92. Case-Forms in the Fourth Declension

The following peculiarities in case-forms of the Fourth Declension require notice:—

a. A genitive singular in -ī (as of the second declension) sometimes occurs in nouns in -tus: as, senātus, genitive senātī (regularly senātūs).

b. In the genitive plural -uum is sometimes pronounced as one syllable, and may then be written -um: as, currum (Aen. 6.653) for curruum.

c. The dative and ablative plural in -ŭbus are retained in partus and tribus; so regularly in artus and lacus, and occasionally in other words; portus and specus have both -ubus and -ibus.

d. Most names of plants and trees, and colus, distaff, have also forms of the second declension: as, fīcus, fig, genitive fīcūs or fīcī.

e. An old genitive singular in -uis or -uos and an old genitive plural in -uom occur rarely: as, senātuis, senātuos; fluctuom.

f. The ablative singular ended anciently in -ūd (cf. § 43. N. 1): as, magistrātūd.