[2496.] After a word ending with a vowel, -m, or -us, the verb est often loses its e: as, bonast, bonumst, bonust, vīsust. So, too, es sometimes loses its vowel: as homo’s, adeptus’. This usage reflects the actual pronunciation of common speech.
[2497.] Semi-hiatus or Semi-elision. A long final vowel is sometimes shortened before a vowel. This may occur either in the arsis ([2520]), or in a resolved thesis: as, án quĭ amant (Verg.); léctulŏ ērudītulī (Cat.); nam quĭ́ aget (Ter.).
This kind of shortening is not frequent except in the early dramatists, who often shorten under the verse-ictus a monosyllable ending in a long vowel and followed by an initial vowel (as in the third example above).
[2498.] Synaloepha (Greek συναλοιφή, a smearing together) is a general term used to denote the means of avoiding hiatus. It includes elision and synizesis, though some grammarians use it in the same sense as synizesis.
[2499.] Synizesis (Greek συνίζεσις, a settling together). Two vowels (or a vowel and a diphthong) which belong to different syllables sometimes coalesce so as to form one syllable. This is called Synizesis, and is especially common in the early dramatists. Examples are: me͡o, e͡adem, cu͡ius, aure͡i. See [117].
Some grammarians would include under Synizesis only cases in which a short vowel is subordinated to a following long; as tu͡o.
[2500.] The term Synaeresis (Greek συναίρεσις, a taking together) is sometimes used as a synonym for Synizesis. The ancient grammarians, however, used it in the sense of Contraction ([118]).
[2501.] Dialysis (Greek διάλυσις, a breaking up). Conversely, two vowels which usually form a diphthong are sometimes separated so as to form two syllables: as coëpī (Lucr.) for coepī.
This, however, is really the survival of the original forms ([120]).
[2502.] The name Diaeresis (Greek διαίρεσις, a separating) is sometimes used as a synonym for Dialysis; but it is better to restrict it to the meaning defined in 2542.