Perfective and Imperfective Verbs

01

How the Pairs Are Built

There are three ways a pair is put together, and a dictionary will always give you both members, so the safest course is to learn them together.

By prefix

The commonest pattern: the imperfective is the bare verb, and a prefix makes it perfective. The prefix adds the sense of completion and nothing else.

• dělat - udělat (to do)
• psát - napsat (to write)
• vidět - uvidět (to see)

• Udělal jsem to.

  I did it.

By a change inside the verb

Here the perfective is the shorter member and the imperfective is built from it, usually with a longer suffix. The direction is the reverse of the pattern above.

• kupovat - koupit (to buy)
• dávat - dát (to give)
• otevírat - otevřít (to open)

• Otevřela dveře.

  She opened the door.

By two different verbs

A small group takes its two members from unrelated roots and simply has to be memorised.

• brát - vzít (to take)

• Vezmu si to.

  I will take it.

02

The Perfective Has No Present

This is the consequence that surprises learners most. An action presented as complete cannot also be going on right now, so a perfective verb has no present tense at all. Its present-shaped forms are its future.

• Kupuji chleba.

  I am buying bread.

• Koupím chleba.

  I will buy bread.

An imperfective verb, having a real present, builds its future the long way instead, with budu and the infinitive.

• Budu kupovat chleba.

  I will be buying bread.

03

Choosing in the Past

Both aspects have a past tense, and both are common. Take the imperfective when the action was a background, a habit or something you were in the middle of.

• Každý den jsem vařil.

  I cooked every day.

• Zrovna jsem vařil.

  I was just cooking.

Take the perfective for one event that came off, especially where a result is still in view.

• Uvařil jsem oběd.

  I have made lunch.

04

Aspect in Commands

A positive command is nearly always perfective: you are asking for the thing to be done, not for the doing of it.

• Otevři okno.

  Open the window.

A negative command reverses this and takes the imperfective, because you are forbidding the activity itself rather than one completed act.

• Neotvírej okno.

  Don't open the window.

05

Recognising the Aspect

No sign is infallible, but three go a long way. A short verb with no prefix is almost always imperfective. Put a prefix on it and it turns perfective. Add a long suffix such as -ovat or -ávat on top of the prefix and it swings back to imperfective, now meaning the repeated version of the prefixed action.

• psát (imperfective) - přepsat (perfective) - přepisovat (imperfective)

• Přepisuji text.

  I am rewriting the text.

06

What Forces the Imperfective

Anything that says how often or how long requires the imperfective, because a single completed event cannot be repeated and cannot last. Words like vždycky, často and celý den settle the choice before you reach the verb.

• Vždycky vařím doma.

  I always cook at home.

• Celý den jsem četl.

  I read all day.

07

After a Modal Verb

Both aspects appear as infinitives after musím, chci and the rest, and they keep their ordinary difference: the imperfective names the activity, the perfective names the job to be finished.

• Musím psát dopisy.

  I have to write letters.

• Musím napsat ten dopis.

  I have to finish that letter.

08

Verbs Outside the System

Verbs of beginning, ending and continuing take an imperfective infinitive after them, since you cannot begin something that is already presented as finished.

• Začínám se učit.

  I am starting to study.

A handful of verbs, most of them borrowed, serve as both aspects at once and take their reading from the sentence around them. Investovat, to invest, is one: the same form can describe what you do now or what you will have done.

• Investuji do akcií.

  I invest in shares. / I will invest in shares.