-ивать

Usage notes
The frequentative and imperfectivizing suffixes are etymologically the same. The spelling-variant suffixes can be distinguished from the other suffixes by their iotation behavior, by the restriction of the second type to certain root-final consonants, and by the types of verbs they usually affect. Note also that in the spelling-variant type, an underlying root consonant that has been modified or deleted may reappear, as in, based on the root подскок-, which appears in iotated form in. For all /-ивать suffixes, the stress is drawn onto the syllable before the suffix, and an о in that syllable usually changes into а.