a. A genitive singular in -í (as of the second declension) sometimes occurs in nouns in -tus: as, senátus, genitive senátí (regularly senátús).
b. In the genitive plural -uum is sometimes pronounced as one syllable, and may then be written -um: as, currum (Aen. vi. 653) for curruum.
c. The dative and ablative plural in -ubus 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, fícus, fig, genitive fícús or fící.
e. An old genitive singular in -uis or -uos and an old genitive plural in -uom occur rarely: as, senátuis, senátuos; fluctuom.
f. The ablative singular ended anciently in -úd (cf. § 43. N. 1): as magistrátúd.