Heavy Construction

The Allen and Greenough is still under construction; so some links may not work quite the way you would expect.

Quantity of Vowels.

a. Vowels. A vowel before another vowel or h is short: as, via, trahó.

NOTE: It was once long in these also: as, plénus fidéí (Ennius, at the end of a hexameter). A is also long before í in the old genitive of the first declension: as, auláí.

NOTE: But many Greek words are more or less Latinized in this respect: as, Académia, chorea, Malea, platea.

5. In d=ius, in eheu usually, and sometimes in Diána and ohe, the first vowel is long.

b. Diphthongs. A Diphthong is long: as, foedus, cui,[1][Rarely dissyllabic cui (as Mart. i. 104. 22).] aula.

Exception. - The preposition prae in compounds is generally shortened before a vowel: as, prae-ustís (Aen. vii. 524), prae-eunte (id. v. 186).

NOTE: U following q, s, or g, does not make a diphthong with a following vowel (see § 5. N. 2). For a-ió, ma-ior, pe-ior, etc., see § 11. d and N.

c. Contraction. A vowel formed by contraction (crasis) is long: as, níl, from nihil; cógó for co-agó; máló for má-voló.

NOTE: Two vowels of different syllables may be run together without full contraction (syniz=esis, § 642): as, deinde (for deinde), meós (for meós); and often two syllables are united by Synaeresis (§ 642) without contraction: as when parietibus is pronounced paryetibus.

d. A vowel before ns, nf, gn, is long: as, ínstó, ínfáns, sígnum.

Quantity of Syllables.

e. A syllable is long if it contains a long vowel or a diphthong: as, cá-rus, ó-men, foe-dus.

f. Position. A syllable is long by position if its vowel, though short, is followed by two consonants or a double consonant: as, adventus, cortex.

But if the two consonants are a mute followed by 1 or r the syllable may be either long or short (common) ; as, alacris or alacris; patris or patris.

Vowels should be pronounced long or short in accordance with their natural quantity without regard to the length of the syllable by position.

NOTE 1: The rules of Position do not, in general, apply to final vowels before a word beginning with two consonants.

NOTE 2: A syllable is long if its vowel is followed by consonant i (except in biiugis, quadriiugis): see § 11. d.

NOTE 3: Compounds of iació, though written with one i, commonly retain the long vowel of the prepositions with which they are compounded, as if before a consonant, and, if the vowel of the preposition is short, the first syllable is long by position on the principle of § 11. e.