Present participles: contract verbs
As you already know from finite verb forms, some verbs have a first principal part with a stem ending in a vowel. As a result, when you add an ending to the first principal part of verbs like ποιέω (stem ποιε-)or ὁράω (ὁρα-), the stem contracts with endings beginning with a vowel.
This is true for participles as well. For active participles in -ων, -ουσα, ον, the stem vowel will contract with -ω-, -ο- and -ου-. For middle or passive participles in -όμενος, -ομένη, -όμενον, the stem will always contract with -ο-.
Stems ending in -ε-
The possible contractions are:
- ε + -ω- -> ω
- ε + -ου- -> ου
- ε + -ο- -> ου
You can figure out the accent in the same way as for finite verbs: identify the syllable that would receive the accent on the unaccented form, do the contraction, then add the accent on the syllable you previously identified. For example, you could form the masculine nominative singular of the present active participle of ποιέω as follows:
- ποιε + ων : accent would fall on -ε- (ποιέων)
- ε + ω == ω, so the form is ποιων ; the epsilon is now part of the contraction, so we’ll put the accent on the contract -> ποιῶν.
The active particple of ποιέω therefore will be ποιῶν, ποιοῦσα, ποιοῦν. The passive participle will be ποιούμενος, ποιουμένη, ποιούμενον.
Stems ending in -α-
- α + -ω- -> ω
- α + -ου- -> ω
- α + -ο- -> ω
The active particple of ὁράω therefore will be ὁρῶν, ὁρῶσα, ὁρῶν. The passive participle will be ὁρώμενος, ὁρωμένη, ὁρώμενον.