[*] 603. The following are General Rules of Quantity (cf. §§ 9-11):
Quantity of Vowels[*] a. Vowels. A vowel before another vowel or h is short: as, vĭa, trăhō . Exceptions.
- In the genitive form -ius,ī is long: as, utrīus , nūllīus . It is, however, sometimes short in verse (§ 113. c).
- In the genitive and dative singular of the fifth declension, e is long between two vowels: as, diēī; otherwise usually short, as in fidĕī , rĕī , spĕī .
- In the conjugation of fīō , i is long except when followed by er . Thus, fīō , fīēbam , fīam , but fĭerī,fĭerem; so alsofĭt (§ 606. a. 3).
- In many Greek words the vowel in Latin represents a long vowel or diphthong, and retains its original long quantity: as, Trōes (Τρῶες),Thalīa (Θαλεῖα). hērōas (ἥρωας), āēr (ἄηρ).
- In dīus , in ē˘heu usually, and sometimes inDī˘āna andō˘he, the first vowel is long.
[*] Note.--Two vowels of different syllables may be run together without full contraction ( synizēsis , § 642): as, deinde (for deinde ), meōs (for meōs ); and often two syllables are united by Synæresis (§ 642) without contraction: as when părĭĕtĭbŭs is pronounced paryĕtĭbus.[*] d. A vowel before ns, nf, gn, is long: as, īnstō , īnfāns , sīgnum .
Quantity of Syllables[*] e. A syllable is long if it contains a long vowel or a diphthong: as, cā-rus , ō-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 alăcris; patris or pătris . 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 3.--Compounds of iaciō , 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.
- obicis hostī (at the end of a hexameter, Aen. 4.549).
- inicit et saltū (at the beginning of a hexameter, Aen. 9.552).
- prōice tēla manū (at the beginning of a hexameter, Aen. 6.836).
[*] Note 4.--The y or w sound resulting from synæresis (§ 642) has the effect of a consonant in making position: as, abietis (abyetis), fluviōrum (fluvyōrum). Conversely. when the semivowel becomes a vowel, position is lost: as, sĭlŭae, for silvae .