Compensatory lengthening

Both word formation and inflection may originate consonant clusters which are difficult to pronounce, thus resulting in the loss of one or more consecutive consonants. Lost consonant duration is usually compensated by lengthening the preceding short vowel and, therefore, called compensatory lengthening.

Compensatory vowel lengthening occurs after:

1. loss of consonantal groups ντ, νδ, νθ;
2. loss of ν;
3. loss of σ preceded by λ, μ, ν, ρ.

The table shows compensatory lengthening outcomes of each short vowel:

When the transformation of ᾱ to η preceded consonantal loss, then ᾰ lengthened to η instead of ᾱ.

Lengthening of ε to ει and of ο to ου can be explained by the fact that ει and ου are graphic conventions to represent long close e and long close o, respectively.