-ува-/-юва-

Secondary imperfectivization is a vital part of the Ukrainian aspectual system. It allows speakers to maintain the specific meaning added by a prefix while shifting the focus from the result to the process.

1. Morphological Rules:

• -ува-: Attached after hard consonants. Example: викон-а-ти (to fulfill, perf.) → викон-ува-ти (to fulfill, imperf.).
• -юва-: Used when the suffix triggers softening of the preceding consonant or follows a vowel. Example: поясн-и-ти (to explain, perf.) → поясн-юва-ти (to explain, imperf.); засво-ї-ти (to internalize, perf.) → засво-юва-ти (to internalize, imperf.).
• -овува-: If the perfective verb already ends in -увати, the imperfective is formed by expanding the suffix to -овувати. Example: застосувати (to apply, perf.) → застосовувати (to apply, imperf.).

2. Consonant Changes (2nd Conjugation Verbs):
When forming the imperfective from 2nd conjugation verbs (ending in -ити), specific consonant mutations occur before the suffix:

• L-epenthesis: If the perfective stem ends in a labial consonant (б, п, в, м, ф), the letter л is inserted, followed by the soft -юва- suffix. Example: встановити → встановлювати; відновити → відновлювати. (Note: Labial stems of other conjugations do not insert 'л' and take the hard -ува-, e.g., приховати → приховувати).
• Mutations: Other consonants mutate (e.g., д → дж, з → ж, т → ч, с → ш). Example: засадити → засаджувати; запросити → запрошувати.

3. Stress and Vowel Alternation:
The stress in these verbs often remains on the root vowel (e.g., вико́нувати, засво́ювати, відно́влювати), though in some verbs it falls on the suffix. For verbs taking the expanded -овува- suffix, the stress almost always falls on the -о- (e.g., застосо́вувати, організо́вувати). While the root vowel 'o' does not change to 'a' (e.g., виконати → виконувати, not *виканувати), Ukrainian has a very common vowel alternation where 'о' and 'е' frequently change to 'і' before -ува-/-юва- when the stress falls on the root vowel (e.g., викоренити → викорінювати, виполоскати → виполіскувати).

4. Usage and Borrowed Verbs:
These verbs are used in the imperfective aspect for ongoing processes or habitual actions. Note that many borrowed verbs ending in -увати (like організувати or гарантувати) are biaspectual, meaning they can function as both perfective and imperfective depending on the context. When a strictly imperfective form is needed, these verbs often expand to the -овува- suffix (e.g., організувати [perf./imperf.] → організовувати [strictly imperf.]).