[142]. e before guttural l ([60]) was changed to o: as, solvō, I undo, from *seluō (se-, as in se-cordia, luō = Greek λύω); culmen, top, for *celmen, from *cellō in ex-cellō; volō, I wish, for *velō; but e is preserved before dental l ([60]): as in velle, velim ([773]). Before l followed by any consonant save l this o changes to u ([141]): as, vult.
[143]. In a number of words, notably in voster, your, vorsus, turned, vortex, eddy, and votāre, forbid, the forms with o were replaced, about the second century B.C. by forms with e: as, vester, versus, vertex, vetāre (Quint. 1, 7, 25).
[144]. In a few cases a vowel is influenced by the vowel of a neighbouring syllable: as,
nisi, unless, for *nesi; iīs, for eīs, to them ([671], [674]); diī, diīs, gods, for deī, deīs ([450]); nihil, nothing, for *nehil; homō, man, for *hemō (cf. nēmō, from ne-hemō, [118]); see also [104, d]; [105, i].
[QUALITATIVE VOWEL GRADATION.]
[145]. The same stem often shows different vowels in different forms. In most of these cases this difference was inherited from a very early period and continued in the Latin. Such old inherited variation of the quality of the stem-vowel is called qualitative vowel gradation. The qualitative variations may be accompanied by quantitative changes ([135]).
Often the verb and the noun are thus distinguished by different vowels: as, tegō, I cover, and toga, a garment, toga; precor, I beg, and procus, suitor, cf. English to sing and a song, to bind, and a bond. The different tenses of some verbs show a like gradation: as, capiō, I take, cēpī; faciō, I make, fēcī, cf. English I sing, I sang; I bring, I brought. The same occurs in derivation: as doceō, I teach, by the side of decet; noceō, I harm, by the side of nex (nec-s). The two vowels which occur most frequently in such gradation are e and o: as in stems in -o-, domine, dominus (for dominos); as variable vowel ([824]); genos (genus, [107, c]) in the nom. sg. by the side of *genes- in the oblique cases (gen. generis for *genesis, [154]); honōs by the side of hones- in hones-tus; modus, measure, for *modos (originally a neuter -s- stem like genus ([487], [491]), but transferred later to the -o- declension), by the side of modes- in modes-tus, seemly. See [187].
[(B.) CONSONANT CHANGE.]
[146]. In a number of words which belong more or less clearly to the stem of the pronoun quo- ([681]), cu- ([157]), the initial c has disappeared before u: as,