([7.]) In the imperial age, ss after long vowels and diphthongs was regularly changed to s: as, clausī, I closed; ūsus, used ([166, 2]); but always ēsse, to eat ([769]); ll changed to l after diphthongs: as, caelum, chisel ([166, 6]); also when preceded by ī and followed by i: as, vīlla, country-place, but vīlicus (adject.); mille, thousand, but mīlia ([642]). Elsewhere ll was retained after long vowels: as, pūllus ([166, 7]), clean; rāllum, ploughshare, from rādō with suffix -lo- ([209]). In Cicero’s time (Quint. 1, 7, 20) the spelling was still caussa ([155, b]), matter; cāssus ([930]), fallen; divīssiō (cf. [912]), division. Vergil also, according to Quintilian, retained the doubled consonants, and the best manuscripts of both Vergil and Plautus frequently show ll and ss for later l and s, as do inscriptions: as, PROMEISSERIT, he might have promised (49 B.C.); ACCVSSASSE, to have accused.
([8.]) After a long vowel d was dropped before consonant u (v): as, svāvis, sweet, for *svādvis from svād- (cf. svādeō).
([9.]) r before st was dropped: as, tostus, roasted ([1004]) for *torstus from the stem tors- (cf. torreo with assimilated -rs-, [166, 8]).
([10.]) -rts- changed to -rs: as, arsī, I burnt, for *artsī ([1000]). -rcsc- changed to -sc-: as, poscō, I demand, for *porcscō ([834]).
([11.]) In ipse, self, for *is-pse, an s has disappeared before -ps-
([12.]) (12.) d (t) disappears between r and c: as, cor-culum for cord(i)-culum ([275]).
[171.] Final Disappearance. (1.) A word never ends in a doubled consonant: as, es for *es-s, thou art, which Plautus and Terence still scan as a long syllable; and the following cases of assimilation: ter for *terr from *ters (cf. terr-uncius, a quarter of an ās, a farthing, [1272], for *ters-uncius, [166, 8]); fār, spelt, for *farr, from *fars ([489]); fel, gall, for *fell, from *fels ([482]); in mīles, soldier, for *mīless from *mīlets (cf. Gen. mīlitis, [477]) the final syllable is still long in Plautus. hoc, this, for *hocc from *hod-c(e)(the neuter *hod from the stem ho-, as istud, illud ([107, c]) from isto-, illo-) counts as a long syllable even in classical poetry.
([2.]) No Latin word can end in two explosives: thus, final t is dropped in lac, milk ([478]); final d in cor, heart ([476]).
([3.]) When final s was preceded by r or l, it was assimilated to these liquids, and final rr and ll were then simplified to r and l. See the examples under (1). Wherever final -rs and -ls appear they are not original but the result of the disappearance of an intervening consonant: as, puls, pottage, for *pults ([533]); pars, part, for *parts ([533]); all with syncope ([111]) of the vowel i in the nominative sg.
([4.]) Original final ns was changed to s and the preceding vowel was lengthened: as, sanguīs, blood ([2452]), for *sanguins from the stem sanguin- ([486]). Wherever final -ns appears it is not original but the result of the disappearance of an intervening consonant: as, ferēns, carrying, for *ferents, from the stem ferent-; frōns, foliage, for *fronds, from the stem frond-.