- Added to verbal stems ending in a consonant to form an action noun.
- Added to o-grade of the verbal stem
- Added to zero-grade of the verbal stem
- Added to e-grade of the verbal stem
In Attic, the suffix takes the form -ᾱ (-ā) after ε (e), ι (i) or ρ (r).
The o-grade and zero-grade derivations have the accent on the suffix.