The noun stem ending is often slightly modified in forming the theme: thus, laud- becomes laudā- in laudō for *laudā-ō, and flōr- becomes flōre- in flōre-ō.
[840.] In many of the forms, the final vowel of the theme is contracted with the variable vowel: as,
plantō, plantās ([118], [3]) for *plantāi̭ō, *plantāi̭es ([153, 2]); monēs for *monēi̭es ([118, 1]), audīs for *audīi̭es ([118, 3]). The long ā, ē, or ī, is regularly shortened in some of the forms: as, scit, arat, habet, for Plautine scīt, arāt, habēt. In a few forms no contraction occurs: as, moneō, audiō, audiu-nt, audie-ntis, &c., audie-ndus, &c. ([114]). Denominatives from stems in -u-, as acuō, are not contracted, and so have the forms of verbs in -ere ([367]).
[841.] The suffix of the present subjunctive of sum, am, is -ī-, which becomes -i- before -m, -t, and -nt: si-m, sī-s, si-t, sī-mus, sī-tis, si-nt ([35, 2, 3]). So also in the singular and in the third person plural, dui-m, &c. ([756]), and edi-m, &c. ([769]), and in all the persons, veli-m, &c. (nōli-m, &c., māli-m, &c.). An old suffix is -iē- (-ie-), in sie-m, siē-s, sie-t, and sie-nt.
[842.] (1.) The present subjunctive stem of verbs in -ere, -ēre, and -īre, ends in -ā-, which becomes -a- in some of the persons; this suffix replaces the variable vowel of the indicative: as,
rega-m, regā-s, rega-t, regā-mus, regā-tis, rega-nt; capia-m, capiā-s, &c.; monea-m, moneā-s, &c.; audia-m, audiā-s, &c. ea-m, quea-m, fera-m, and the old fua-m ([750]), also have the formative subjunctive vowel.
[843.] (2.) The present subjunctive stem of verbs in -āre ends in -ē-, which becomes -e- in some of the persons: as,
laude-m, laudē-s, laude-t, laudē-mus, laudē-tis, laude-nt. dō, give, also has de-m, dē-s, &c.