The aspect overview presents the tidy picture: nearly every verb is one half of an imperfective/perfective pair, and you choose between the halves constantly. That picture is true for the overwhelming majority of verbs — but a sizeable minority do not fit it, and they are exactly the ones that ambush learners who expect every verb to have a partner. This page covers the three classes that break the pattern: biaspectual verbs (one form does the work of both aspects), imperfective-only verbs (no perfective partner exists), and perfective-only verbs (no imperfective partner exists) — plus the semelfactive -ну- verbs, which look like a special perfective but encode something English has no single word for: a single instantaneous flick of an action.
Biaspectual verbs (двовидові дієсло́ва)
A biaspectual verb has one form that functions as both imperfective and perfective; the aspect is read off the context, not the verb. There is no second form to switch to — телефонува́ти is, by itself, both "to be calling" and "to call (and get through)." This is genuinely unusual: the verb refuses to commit to a viewpoint until the sentence around it forces one.
The largest and most living group is borrowed verbs in -ува́ти: телефонува́ти, організува́ти, атакува́ти, гарантува́ти, реалізува́ти, інформува́ти, ліквідува́ти, телеграфува́ти, адресува́ти, веле́ти (a native one). Because these entered the language without a built-in aspectual partner, a single form carries both jobs.
Я телефону́ю тобі́ щовечора, а ти ніко́ли не бере́ш слу́хавку.
I call you every evening, and you never pick up. (Repetition → imperfective reading of телефону́ю.)
Почека́й хвили́нку, я телефону́ю в банк і одра́зу поверну́ся.
Hang on a second, I'll call the bank and come right back. (Single bounded future act → perfective reading of the SAME form.)
Notice that nothing in the verb changed between those two sentences — щовечора ("every evening") pulled it toward the imperfective, while почека́й + одра́зу ("hang on / right away") pulled it toward a single completed call. The form телефону́ю is doing what прочита́ю and чита́ю do with two separate words.
Ця ка́мера автомати́чно гаранту́є я́кість зо́браження.
This camera automatically guarantees image quality. (General property → imperfective.)
Я гаранту́ю, що за́втра все бу́де гото́ве.
I guarantee that everything will be ready tomorrow. (A single act of giving a guarantee, now → perfective.)
The drift toward pairs
The biaspectual class is not stable. For several high-frequency loanwords, Ukrainian has grown a secondary imperfective in -о́вувати, leaving the original -ува́ти form increasingly perfective. So організува́ти is splitting into a pair:
| Tending imperfective | Tending perfective | Meaning |
|---|---|---|
| організо́вувати | організува́ти | to organize |
| реалізо́вувати | реалізува́ти | to implement / sell |
| ліквідо́вувати | ліквідува́ти | to eliminate |
For these you can often treat the verb as a real pair; for purer biaspectuals (телефонува́ти, гарантува́ти, атакува́ти, інформува́ти, веле́ти) you cannot — there is only the one form. This is the honest, messy state of the language: a productive loan-suffix that historically didn't mark aspect is being retrofitted into the pair system one verb at a time, and different speakers are at different points in that drift.
Воро́жа авіа́ція атакува́ла мі́сто всю ніч.
Enemy aircraft were attacking the city all night. (Duration 'all night' → imperfective reading of атакува́ла.)
О сьо́мій ра́нку проти́вник атакува́в наші́ пози́ції і про́рвав оборо́ну.
At seven in the morning the enemy attacked our positions and broke through the defenses. (Single event in a sequence → perfective reading of the same атакува́в.)
Imperfective-only verbs (imperfectiva tantum)
Some verbs have no perfective partner at all — you cannot "complete" them, because they denote states or open-ended activities with no inherent boundary. There is no whole-event viewpoint to take of "having" or "being able," so the perfective slot is simply empty.
The core group is the statives — and they happen to be among the most frequent verbs in the language:
| Verb | Meaning | Why no perfective |
|---|---|---|
| бу́ти | to be | a state, not an event |
| ма́ти | to have | possession is open-ended |
| могти́ | to be able / can | an ability, no endpoint |
| хоті́ти | to want | a state of desire |
| зна́ти | to know | a state of knowledge |
| нале́жати | to belong | a relation, not an act |
| зна́чити | to mean | a relation |
Alongside these sit the verbs of bodily position and continuous activity: сиді́ти ("to sit"), стоя́ти ("to stand"), лежа́ти ("to lie"), спа́ти ("to sleep"), жи́ти ("to live"), люби́ти ("to love"), and also indeterminate motion verbs like бі́гати ("to run around"). All name something that simply goes on, with no built-in finish line.
Я ма́ю двох браті́в і одну́ сестру́.
I have two brothers and one sister. (ма́ти — imperfective only; there is no perfective 'to have'.)
Він живе́ в Льво́ві вже два́дцять ро́ків.
He has lived in Lviv for twenty years now. (жи́ти — a state, no perfective.)
Я не мо́жу зрозумі́ти, чому́ ти так хо́чеш туди́ пої́хати.
I can't understand why you want to go there so badly. (могти́ and хоті́ти are both imperfective-only statives.)
A subtlety worth flagging honestly: a prefixed form like захоті́ти ("to come to want, to take a fancy to") does exist and is perfective — but it is not a perfective "to want"; it names the onset of the desire, a different meaning. The state хоті́ти itself has no perfective. Likewise полюби́ти ("to come to love") is the onset of люби́ти, not its completion. So when you see a prefixed partner for a stative, check whether it really means the same thing finished, or — as here — the beginning of the state, which is a separate event.
Perfective-only verbs (perfectiva tantum)
The mirror image is rarer but real: a handful of verbs are perfective only, with no imperfective partner. They denote something that is intrinsically a sudden, bounded result — there is no "ongoing process" version to make imperfective.
- опини́тися "to end up / find oneself (somewhere)" — you don't gradually "be ending up"; you suddenly are there.
- розговори́тися "to get talking / warm up into a conversation" — the prefix роз- + -ся names the onset-and-launch of talking as a single event.
- розхвилюва́тися "to get worked up / agitated," схамену́тися "to come to one's senses," спам’ятува́тися "to recollect oneself."
Я й не помі́тив, як опини́вся на тому́ кінці́ мі́ста.
I didn't even notice how I ended up at the other end of town. (опини́тися — perfective only; a sudden result, no process form.)
Споча́тку він мовча́в, а по́тім розговори́вся і не міг зупини́тися.
At first he was silent, and then he got talking and couldn't stop. (розговори́тися — the launch of talking, perfective only.)
Semelfactive -ну- verbs: a single instantaneous act
The most useful class on this page for everyday speech is the semelfactive (одноразо́ве, "one-time") in -ну-. A semelfactive denotes one single, quick, instantaneous occurrence of an action that the imperfective presents as repeated or continuous. It pairs with a multiplicative imperfective in -а-:
| Imperfective (multiplicative) | Semelfactive (-ну-) | Contrast |
|---|---|---|
| сту́кати | сту́кнути | to be knocking / to knock once |
| крича́ти | кри́кнути | to be shouting / to give one shout |
| маха́ти | махну́ти | to be waving / to give one wave |
| стриба́ти | стрибну́ти | to be jumping / to give one jump |
| зітха́ти | зітхну́ти | to be sighing / to give one sigh |
| кашля́ти | ка́шлянути | to be coughing / to cough once |
The semelfactive is perfective (it is a single completed micro-event), so it has no present and its present-shaped form is future: сту́кну = "I'll give one knock." The meaning English needs a whole phrase for — "give a shout," "knock once," "a single wave" — Ukrainian packs into the -ну- suffix.
Хтось сту́кнув у две́рі — піди́ подиви́ся, хто там.
Someone knocked at the door — go see who's there. (сту́кнув — one single knock, semelfactive perfective.)
Ці́лу ніч хтось сту́кав за стіно́ю, я не міг засну́ти.
All night someone was knocking behind the wall, I couldn't fall asleep. (сту́кав — repeated, ongoing knocking, multiplicative imperfective.)
Вона́ махну́ла руко́ю на проща́ння і зни́кла в нато́впі.
She gave a wave goodbye and vanished into the crowd. (махну́ла — one wave; маха́ти would be 'was waving'.)
Він кри́кнув від бо́лю, коли́ нога́ підверну́лася.
He cried out in pain when his foot twisted. (кри́кнув — a single shout; крича́ти 'be shouting' would be the process.)
For the full mechanics of how the -ну- suffix is attached and where the stress lands, see semelfactive -ну- verbs.
Source-language comparison
For an English speaker, the entire idea that a verb might lack a partner is foreign, because English doesn't have aspect pairs to begin with. The biaspectual class is the easiest to accept — "call" in English is also vague between "I'm calling" and "I'll call," and телефонува́ти behaves the same way. The hard part is the opposite intuition: English freely says "I finished having lunch," and a learner reaches for a perfective of "to have" or "to know" that does not exist. The statives бу́ти, ма́ти, могти́, хоті́ти, зна́ти are imperfective only, full stop. The semelfactive -ну- is where English is genuinely poorer: English has no single word for "knock exactly once" or "give one wave," so you must learn to hear -ну- as "a single flick of the action."
For a Russian speaker, all four classes transfer in their architecture — biaspectuals, imperfectiva/perfectiva tantum, and the semelfactive -ну- all exist in Russian too. Relearn the specific lexical members: Ukrainian веле́ти, телефонува́ти, the -ува́ти loan class, and the standard Ukrainian forms (могти́ not the Russian мочь-stem, хоті́ти, ма́ти). And note that Ukrainian's secondary imperfectives often surface as -о́вувати (організо́вувати), a spelling and stress you should not import wholesale from Russian.
Common Mistakes
❌ Я бу́ду проорганізува́ти зу́стріч. (inventing a perfective + бу́ду)
Wrong on two counts — there's no prefix needed and бу́ду takes only imperfectives. The biaspectual covers the future: Я організу́ю зу́стріч.
✅ Я організу́ю зу́стріч.
I'll organize the meeting — the biaspectual form, perfective reading from context.
❌ Я поматну́ книжки́. (looking for a perfective of 'to have')
There is no perfective of ма́ти — it is imperfective only. Use the compound future: Я бу́ду ма́ти книжки́ / У ме́не бу́дуть книжки́.
✅ У ме́не бу́дуть книжки́.
I'll have the books — ма́ти is imperfective only, so the future is compound.
❌ Він сту́кав у две́рі оди́н раз. (multiplicative for a single act)
A single knock is the semelfactive: Він сту́кнув у две́рі оди́н раз. The form сту́кав means repeated/ongoing knocking.
✅ Він сту́кнув у две́рі оди́н раз.
He knocked at the door once — semelfactive сту́кнути for a single instantaneous act.
❌ Я бу́ду зна́ти відповідь за́втра, а сього́дні зна́тиму погано. (treating зна́ти as if it had a perfective result form)
зна́ти is imperfective only; for 'I'll find out / get to know' use a different verb, дізна́тися: Я дізна́юся відповідь за́втра.
✅ Я дізна́юся відповідь за́втра.
I'll find out the answer tomorrow — дізна́тися is the perfective of дізнава́тися 'to find out', not of зна́ти 'to know'.
Key Takeaways
- Biaspectual verbs (двовидові) have one form for both aspects; context decides. The big group is -ува́ти loanwords: телефонува́ти, організува́ти, атакува́ти, гарантува́ти, реалізува́ти, інформува́ти, веле́ти. Some are drifting into real pairs via secondary imperfectives in -о́вувати.
- Imperfective-only verbs (imperfectiva tantum) are the statives: бу́ти, ма́ти, могти́, хоті́ти, зна́ти, нале́жати, плюс сиді́ти, стоя́ти, лежа́ти, спа́ти, жи́ти, люби́ти. No perfective exists; prefixed forms like захоті́ти name the onset, a different meaning.
- Perfective-only verbs (perfectiva tantum) are rarer: опини́тися, розговори́тися, схамену́тися — intrinsically sudden, bounded results.
- Semelfactive -ну- verbs (сту́кнути, кри́кнути, махну́ти, стрибну́ти) are perfectives meaning a single instantaneous act, paired against multiplicative imperfectives (сту́кати, крича́ти, маха́ти) for the repeated/ongoing version.
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- Verbal Aspect: The Big PictureA2 — Aspect is the central, pervasive feature of the Ukrainian verb: nearly every verb belongs to an aspect PAIR — imperfective (недоко́наний вид), which views an action as a process, ongoing, repeated, or general (чита́ти), and perfective (доко́наний вид), which views it as a single completed whole with a result or boundary (прочита́ти). The consequences are sharp: imperfectives have a present, a past, and BOTH futures (бу́ду чита́ти / чита́тиму); perfectives have NO present — their present-shaped form is future (прочита́ю = 'I will read it through') — only a past (прочита́в) and a simple future (прочита́ю). Aspect is chosen for EVERY verb in EVERY clause; it is not optional, and it has no English equivalent.
- Semelfactive -ну- Verbs (a single act)B2 — The -ну- suffix carves a SEMELFACTIVE out of a repeatable action — one instantaneous instance: кри́кнути 'give one shout' beside крича́ти 'be shouting', сту́кнути 'knock once' beside сту́кати, махну́ти 'give one wave' beside маха́ти. These -ну- verbs are perfective and punctual; this page sets them against their multiplicative -а- imperfectives and notes the -ну- verbs that drop the suffix in the past (мерзнути → мерз).
- Forming Aspect Pairs: PrefixesB1 — The most common way to build a perfective is to add a 'pure' perfectivizing prefix to the imperfective: чита́ти→прочита́ти, писа́ти→написа́ти, роби́ти→зроби́ти, ї́сти→з’ї́сти, пи́ти→ви́пити. The frequent perfectivizing prefixes are про-, на-, з-/с-/зі-, по-, ви-, при-. The catch: the SAME prefixes can instead add lexical meaning and make a NEW verb (писа́ти→переписа́ти 'rewrite'), so you must learn to tell aspect-only prefixation from meaning-changing prefixation.
- Imperfective vs Perfective: The Master DecisionB1 — A decision-tree for the single hardest choice in Ukrainian: which aspect. Order the diagnostic questions and most decisions are made for you before you ever weigh 'process vs result' — present/ongoing, repeated/habitual, duration, and phase verbs FORCE the imperfective; a single completed result or one event in a sequence forces the perfective. Worked mini-cases, minimal pairs, and the top-five aspect traps.
- Мати (to have)A1 — Complete conjugation-and-usage reference for ма́ти 'to have' — present ма́ю / ма́єш / ма́є / ма́ємо / ма́єте / ма́ють + ACCUSATIVE object, past мав / ма́ла / ма́ло / ма́ли, future both ways (бу́ду ма́ти and synthetic ма́тиму). Covers the rivalry with у ме́не є, the negation нема́є + GENITIVE, obligation ма́ти + infinitive, and the idioms ма́ти ра́цію 'be right', ма́ти на ува́зі 'mean', не ма́є значе́ння.
- Бути (to be)A1 — Complete conjugation-and-usage reference for бу́ти 'to be' — the most important irregular verb in Ukrainian. The present is normally OMITTED (є survives only for existence, possession у ме́не є, and emphasis); the past is gendered був / була́ / було́ / були́; and бу́ду / бу́деш / бу́де / бу́демо / бу́дете / бу́дуть is both the verb's own future and the universal future auxiliary. Predicate nouns are NOMINATIVE in the present but INSTRUMENTAL in the past, future and infinitive.