[2442.] (a.) Final o is short in the nominatives ego, duo. It is sometimes shortened in homo ([130, 3]) and in the nominative of other stems in -n- ([484], [485]): as, mentio, Nāso, virgo. o is regularly short in endo, in the ablatives cito and modo, used as adverbs, and in many other words in late poetry: as, īlico, immo, ergo, quando, octo, &c.; very rarely in the ablative of the gerund.
[2443.] (b.) Before Ovid, o of the present indicative is regularly long. It is shortened only in the following words ([130, 3]): in
volo, six times (Cat., 4 times; Hor., Prop.).
scio, twice (Verg.).
nescio, six times (Verg., twice; Hor., twice; Tib., Prop.);
and once each in eo and veto (Hor.), dēsino (Tib.), and findo (Prop.). From Ovid on, short o is not uncommon.
Short o in other forms of the verb is rare: as, dīxero (Hor.); esto, ero, dabo (Ov.); but o is always short in the imperative cedo, give, tell.
Exceptions in u.
[2444.] Final u is short in indu and noenu.
Exceptions in i.