§603. General Rules

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.

b. Diphthongs. A Diphthong is long: as, foedus, cui,¹ aula.

Exception.—The preposition prae in compounds is generally shortened before a vowel: as, praĕ-ustīs (Aen. 7.524), praĕ-eunte (id. 5.186).

c. Contraction. A vowel formed by contraction (crasis) is long: as, nīl, from nihil; cōgō for †co-agō; mālō for mā-volō.

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.

• 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).

Later poets sometimes shorten the preposition in trisyllabic forms, and prepositions ending in a vowel are sometimes contracted as if the verb began with a vowel.

• (1) cūr an|nōs ŏbĭ|cis (Claud. iv C. H. 264).
• (2) reīcĕ că|pellās (Ecl. 3.96, at end).