Vowel Contractions
If a verb stem ends on either ε, ο, or α, then adding the ending to such a stem, forces this vowel to contract with the first vowel (or a diphthong) of the ending. As a result, another vowel or diphthong appears in place of those two, and often the accent turns into a circumflex.
The rules of contraction can be summarized in the following table, where the rows correspond to the last stem vowel, the columns the first vowel of the ending and the intersection gives the result of the contraction:
One could also express the laws of contraction equivalently using a set of rules (3 rules per vowel) as follows:
Contraction happens in the following cases:
Contract verbs. The present stem of such verbs ends in ε, ο, or α. In the dictionary, they are written in the uncontracted form. Examples of such verbs are ποιέω, σταυρόω, and ἀγαπάω. Here are their conjugation tables for Present Indicative Active (the forms are already contracted):
And for Present Indicative Middle\Passive:
Also see the contracted forms of the Imperfect Active Indicative:
And Imperfect Middle\Passive Indicative:
Liquid verbs. The present stem of these verbs ends in a liquid consonant, i.e. ν, μ, λ, or ρ. The uncontracted future stem of such verbs tends to end on ε. For example, κρίνω is a Present Active Indicative form of the verb and κρινέω is an uncontracted Future Active Indicative form. After contraction, the conjugation table for the Future Indicative Active looks as follows (see more about liquid verbs here):
And for Future Indicative Middle, as follows:
