A syllable is short when it contains a short vowel followed by a vowel or a single consonant: θε-ός
A syllable is long by nature when it contains a long vowel or a diphthong: χώ-ρα_
A syllable is long by position when its vowel precedes two consonants or a double consonant: ἵππος
a. One or both of the two consonants lengthening a final syllable by position may belong to the next word: ἄλλο_ς πολί_της, ἄλλο_ κτῆμα.
b. Length by position does not affect the natural quantity of a vowel. Thus, both λέ-ξω
ϝ may be one of the two consonants: πρός (ϝ) οἶκον (¯ ¯ ˘).145
A stop with a liquid after a short vowel need not make the preceding syllable long by position. A syllable containing a short vowel before a stop and a liquid is common (either short or long). When short, such syllables are said to have weak position.
Thus, in δάκρυ, πατρός, ὅπλον, τέκνον, τί δρᾷ the first syllable is either long or short as the verse requires. In Homer the syllable before a stop with a liquid is usually long; in Attic it is usually short.
a. The stop and the liquid making weak position must stand in the same word or in the same part of a compound. Thus, in ἐκ-λύ_ω
b. β, γ, δ before μ, or ν, and usually before λ, make the preceding syllable long by position. Thus, ἁγνός (¯˘)
N.—‘Common’ quantity has been explained as due to a difference in syllabic division. Thus, in τέ_κνον, the first syllable is closed (τέκ-νον); while in τεκνον the first syllable is open (τέ-κνον). Cp. cross141.146
The quantity of most syllables is usually apparent. Thus, syllables
a. with η, ω, or a diphthong, are long.
b. with ε, ο, before a vowel or a single consonant, are short.
c. with ε, ο, before two consonants, or a double consonant, are long.
d. with α, ι, υ, before two consonants, or a double consonant, are long.
N.—But syllables with ε, ο, or α, ι, υ before a stop and a liquid may be short ( cross145). Cp. also 147 c.146D
In Hom. an initial liquid, nasal, and digamma (3) was probably doubled in pronunciation when it followed a short syllable carrying the rhythmic accent. Here a final short vowel appears in a long syllable: ἐνὶ μεγάροισι (˘[macrdot]˘˘[macrdot]˘), cp. cross28 D. The lengthening is sometimes due to the former presence of ς or ϝ before the liquid or nasal: ὅτε λήξειεϝ (˘[macrdot]¯[macrdot]˘) (cp. ἄλληκτος
The quantity of syllables containing α, ι, υ before a vowel or a single consonant must be learned by observation, especially in poetry. Note, however, that α, ι, υ are always long
a. when they have the circumflex accent: πᾶς, ὑ_μῖν.
c. ι and υ are generally short before ξ (except as initial sounds in augmented forms, cross435) and α, ι, υ before ζ. Thus, κῆρυξ, ἐκήρυξα, πνιξω, ἁρπαζω, ἐλπιζω.147D
α, ι, υ in Hom. sometimes show a different quantity than in Attic. Thus, Att. καλός, τινω, φθανω, λύ_ω, ἵ_ημι, Hom. κα_λός, τί_νω, φθά_νω ( cross28), and λυω and ἵημι usually.148
A vowel standing before another vowel in a Greek word is not necessarily short (as it usually is in classical Latin).148D
1. In Hom., and sometimes in the lyric parts of the drama, a syllable ending in a long vowel or diphthong is shortened before an initial vowel: ἄξω ἑλών ([macrdot]˘˘[macrdot]), εὔχεται εἶναι ([macrdot]˘˘[macrdot]¯), κλῦθί μευ ἀργυρότοξ' ([macrdot]:˘˘[macrdot]˘˘[macrdot]). Here ι and υ have become semivowels ( cross20, cross43); thus, εὔχετα | yεἶναι, cp. cross67. -ᾳ, -ῃ, -ῳ were shortened like α_, η, ω. Thus, ἀσπέτῳ ὄμβρῳ ([macrdot]˘˘[macrdot]¯).
2. This shortening does not occur when the rhythmic accent falls upon the final syllable: ἀντιθίῳ Οδυσῆι ([macrdot]˘˘[macrdot]˘˘[macrdot]˘), ᾧ ἔνι ([macrdot]˘˘).
3. The shortening rarely occurs in the interior of a word. Thus, Hom. ἥρωος (¯˘˘), υἱόν (˘˘), in the Attic drama αὑτηΐ (¯˘¯), τοιοῦτος (˘:¯˘), ποιῶ (˘¯), often written ποῶ in inscriptions (cp. cross43).
Herbert Weir Smyth [n.d.], A Greek Grammar for Colleges; Machine readable text [info] [word count] [Smyth].