Vowel Contraction, Lengthening, and Stretching
Introduction
Vowels can combine and contract (εε > ει, οο > ου), lengthen according to ablaut (ε > η, ο > ω), or stretch to compensate for the droppage of consonants (ε > ει, ο > ου).
Intermediate
Vowel Contraction
Vowel contraction is when two contiguous vowels forming separate syllables combine to create a single syllable. In Attic, vowels contract as follows (dialectical alternatives are given in parentheses):
αα contracts to α
αε contracts to α or η
αο contracts to ω (in Ionic, αο contracts to αυ)
εα contracts to α or η
εε contracts to ει
εη contracts to η
εο contracts to ου
οα contracts to ω
οε and οο contract to ου (in Ionic, εο contracts to ευ)
ωα, ωε, ωο, αω, εω, οω all contract to ω (in Doric, αω contracts to α)
Put another way, in Attic these vowels may be the result of contraction:
ᾱ may be a contraction of αε or εα
ει may be a contraction of εε or εει
η may be a contraction of αε, εα, or εη
ου may be a contraction of οο, εο, or οε
ω may be a contraction of αο, αω, εω, ωα, or ωε
In Ionic, the following diphthongs may be the result of contraction:
αυ may be a contraction of αο
ευ may be a contraction of εο
The letters ι and υ alone are never the result of contraction.
Vowel Lengthening
Vowel lengthen due to ablaut in the following way:
ε > η
ο > ω
See ablaut for more.
Vowel Stretching
Short vowels “stretch” when a subsequent liquid (λ, ρ) or nasal (μ, ν) drops. Grammarians call this “compensatory lengthening,” but Reading Morphology prefers “stretching” to avoid confusion with lengthening due to ablaut. It is also descriptive: when a liquid or nasal drops, we may imagine the vowel stretching to fill the quantitative gap left behind.
In Attic and Ionic, short vowels stretch in the following way:
α > long α or η (αι in Aeolic)
ε > ει
ι > long ι
ο > ου (οι in Aeolic)
υ > long υ
Long vowels don’t stretch.
reading morphologically 