Imperfective and perfective aspect pairs

English has one verb cook and changes the grammar around it: I cook, I am cooking, I cooked, I have cooked. Serbian does something different. For almost every action it has two verbs, and you choose between them depending on how you look at the action. Kuvati is the action of cooking: what you are busy with, what you do every day, the process. Skuvati is the same action seen as a finished whole with a result: the lunch is done and on the table. Both mean "cook", but they are two separate dictionary words, each with its own conjugation.

This is called verb aspect. The process verb is the imperfective, the whole-action verb is the perfective, and the two together are an aspect pair. Nearly every Serbian verb belongs to such a pair, so from now on every new verb you meet is best learnt with its partner.

Some pairs from the kitchen

How a pair is built

Look at the table again and you will see two patterns. In the first group the imperfective is the plain verb and the perfective adds a prefix: kuvati → s-kuvati, peći → is-peći, seći → i-seći, mešati → pro-mešati, prati → o-prati, praviti → na-praviti, jesti → po-jesti. Which prefix a verb takes is not predictable — s-, is-, po-, na-, o-, pro- all occur — so the prefix has to be learnt with the verb.

In the second group it is the other way round: the perfective is the short basic verb and the imperfective is made longer with a suffix: dodati → dodavati, kupiti → kupovati, otvoriti → otvarati. These longer imperfectives usually conjugate as e-class verbs with a changed stem (dodajem, kupujem), while their short perfective partners keep their own class (dodam, kupim).

A good rule of thumb: a verb with an extra prefix in front is nearly always the perfective; a verb made longer with -ava-/-iva-/-ova- in the middle is nearly always the imperfective.

What each member means

• Imperfective — the action as an activity: in progress right now (Kuvam ručak — I am cooking lunch), repeated or habitual (Svaki dan kuvam — I cook every day), or simply the activity itself with no interest in whether it gets finished (Volim da kuvam — I like cooking).
• Perfective — the action as one complete event with a result: the lunch gets cooked, the onion gets chopped, the cake comes out of the oven. It is the verb you use to say something got done: in a command (Skuvaj supu!), in the future (Skuvaću supu), or after da, kad and ako (Hoću da skuvam supu).

The trap: the perfective present is not "now"

Both verbs have a present tense, and both are conjugated normally: kuvam, kuvaš, kuva… and skuvam, skuvaš, skuva…. But a perfective present never describes what is happening at this moment. Skuvam supu on its own does not mean "I am cooking soup" — a finished whole cannot be in progress. To say what you are doing right now, the imperfective is the only option: Kuvam supu.

So where does the perfective present go? It lives inside a bigger sentence, after a word that points forward: after da (Hoću da skuvam supu — I want to cook the soup), after kad or ako (Kad skuvam supu, zvaću te — when I have cooked the soup I will call you), or it becomes a command (Skuvaj supu) or a future (Skuvaću supu). In all of those the action is still to be completed, which is exactly what the perfective is for.

Not every command is perfective and not every present is imperfective — an imperfective command tells someone to keep doing something (Mešaj polako! — keep stirring slowly), and the imperfective has a future too (Kuvaću ceo dan). The question to ask is always the same: am I talking about the activity, or about the thing getting done? How aspect works in past stories — I was cooking against I cooked — is the next lesson.