([1.]) Instances of this are prō for *prōd ([149]; cf. prōdesse) and pro- (Greek πρό); nē and ne- in nescius; the couples regō, I rule, and rēxī; vehō, I draw, vēxī; veniō, I come, vēnī, where the long vowel is characteristic of the perfect stem ([862]); vocō, I call, and vōx, voice; regō, I rule, and rēx, ruler; legō, I read, and lēx, bill; sedeō, I sit, and sēdēs, seat; fidēs, confidence, and fīdō, I trust; dux (cf. ducis), leader, and dūcō, I lead, where verb and noun are differentiated by the quantity of the root vowel; and many others.
([2.]) Sometimes the reduction of the vowel in certain forms amounts to complete loss, as in the adverbial ending -is- in magis ([346], [363]) compared with the comparative suffix -ios, -iōs (Nom. -ior, Genit. -iōris); in the oblique cases of the stem carōn- (nomin. sg. carō, [497]), where the suffix becomes -n- ([545]), genitive car-n-is; in the suffix -ter, which becomes -tr- in all cases but the nom. sg. (pater, patris, etc., [470], [487]); in the feminine -tr-ī-c- to the suffix -tor-; but the nom. sing. Caecīlis ([465]) for Caecīlios is probably due to syncope.
[136]. ([1.]) i before an r which goes back to an earlier voiced s ([154]) was changed to e: as, cineris, of ashes, for *cinisis, from the stem cinis ([491]); Faleriī, for *Falisiī, cf. Falis-cus; (formed like Etrūria, for *Etrūsia, cf. Etrūs-cī).
([2.]) In the nominative singular of compounds like iūdex, judge (from iūs and dīcere), comes, companion (from com, with, and īre, go), the i of the second member of the compounds is changed to e ([470]) after the analogy of words like artifex, artisan, etc. ([107, d]).
[137]. e before -gn- became i: as, īlignus, from the stem īlec- (cf. īlex).
[138]. e before the guttural nasal ([62]) followed by a guttural mute was changed to i: as, septingentī, from septem; singulī, from the stem sem- in semel (for the assimilation of m see [164], 3); obtingō ([925]), I attain, for *óbtengō ([104, c]) from *ob-tangō ([104, e]).
[139]. A similar change took place in the group -enl- which became first -inl- and then -ill-: as, *signilum, diminutive of sīgnum (for ī, see [122], c), first changed by syncope ([111]) from *signilum to *sign̥lum, then to *sigenlum ([172, 3]), then to *siginlum, and finally to sigillum.
[140]. o before nc became u: as, homunculus, manikin for *homonculus, from the stem homon- ([485]); nūncupāre, name, for *nōn-cupāre (nōn- for nōm- ([164, 3]) = syncopated nōmen); hunc, him, for *honc, from hom-ce ([662]).
[141]. o before l followed by any consonant save l was changed to u: as, cultus, tilled, for *coltus, from colere; multa, fine, for old Latin molta. But o before ll is retained: as, collis, hill.