Forming Perfectives with Prefixes | Czech Grammar

Most Czech verbs come in an aspect pair: an imperfective form that views the action as a process or habit, and a perfective form that views it as a single completed whole. The single most common way that pair is built is by sticking a prefix onto a simple imperfective verb. Psát "to write" becomes napsat; vařit "to cook" becomes uvařit. This page shows you how prefixation makes perfectives, which prefixes do the job, and the one fact that trips up every learner: you cannot predict which prefix a given verb wants.

The basic mechanism

Take a simple imperfective verb — psát, dělat, číst, vařit, pít — and add a one- or two-letter prefix. The result is its perfective partner. The two verbs mean the same thing; only the aspect changes.

Imperfective	prefix	Perfective	Meaning
psát	na-	napsat	to write
dělat	u-	udělat	to do / make
vařit	u-	uvařit	to cook
číst	pře-	přečíst	to read
pít	vy-	vypít	to drink (up)
jíst	s-	sníst	to eat (up)
platit	za-	zaplatit	to pay
volat	za-	zavolat	to call

The cleanest way to feel the contrast is to swap only the aspect and watch the meaning shift from process to finished result.

Vařím polévku.

I'm cooking soup (right now, in progress).

Uvařil jsem polévku.

I cooked the soup (it's done — here it is).

Píšu úkol.

I'm doing my homework (in progress).

Napsal jsem úkol.

I did my homework (it's finished).

In each pair the prefixed verb adds nothing to the dictionary meaning — uvařit is not a special kind of cooking, napsat is not a special kind of writing. The prefix simply packages the action as one complete event with an endpoint. That is what "perfectivizing" means.

The "empty" prefix

A prefix that does nothing but change the aspect is traditionally called an empty prefix (or purely perfectivizing prefix). It is "empty" of lexical content: it adds no new meaning, no direction, no nuance. For most simple verbs, exactly one prefix plays this empty role, and that prefix-plus-verb is the verb's official perfective partner.

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An empty prefix changes how the action is viewed (process → completed whole) without changing what the action is. Napsat is just the finished-event version of psát — not "to write on something" or "to write down." Compare this with prefixes that genuinely add meaning, covered below.

For these everyday verbs, the empty prefix has hardened into the standard pair:

Zítra ti zavolám.

I'll call you tomorrow (one completed call).

Konečně jsem přečetl tu knihu.

I finally read that book all the way through.

Vypij to, než to vychladne.

Drink it up before it gets cold.

Snědl jsem celou pizzu sám.

I ate the whole pizza by myself.

The frequent perfectivizing prefixes

There is no single "default" perfectivizing prefix. Several prefixes do this job, and which one a verb takes is a property of that verb. The common perfectivizing prefixes are:

Prefix	Example pair	Meaning
na-	psát → napsat	to write
u-	dělat → udělat; vařit → uvařit	to do; to cook
z- / s-	jíst → sníst; ničit → zničit	to eat up; to destroy
vy-	pít → vypít	to drink up
po-	děkovat → poděkovat; chválit → pochválit	to thank; to praise
pro-	číst → pročíst; budit → probudit	to read through; to wake (someone)
do-	dělat → dodělat	to finish doing
za-	platit → zaplatit; volat → zavolat	to pay; to call
pře-	číst → přečíst	to read

A quick word on the z-/s- prefix, which is genuinely messy. Historically z- perfectivized and s- meant "off / down / together," but modern spelling fixed the prefix as z- in most new perfectives (zničit "to destroy," zhasnout "to switch off") while a closed set keeps the older s- spelling (sníst "to eat up," sebrat "to gather," spálit "to burn up"). There is no rule you can hear; the spelling is lexical, so learn each verb's spelling with the verb.

Poděkoval jsem jí za pomoc.

I thanked her for the help.

Zaplať to kartou, prosím.

Pay for it by card, please.

Musíš ten úkol dnes dodělat.

You have to finish that assignment today.

You cannot guess which prefix is the empty one

This is the hard part, and there is no logical shortcut — so the honest advice is to memorize the perfective partner together with the verb, exactly as you would memorize a noun's gender. The empty prefix is not predictable from the verb's shape or meaning.

Look at two verbs that are almost identical in form and register:

Imperfective	Perfective	Prefix
psát "write"	napsat	na-
číst "read"	přečíst	pře-

Writing and reading are the two halves of literacy, yet writing takes na- and reading takes pře-. Nothing about the verbs predicts this. Vařit takes u- (uvařit), platit takes za- (zaplatit), děkovat takes po- (poděkovat) — each verb simply has its partner, and you have to know it.

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Treat the perfective partner as a second dictionary form. When you learn psát, learn "psát / napsat" as a unit, the way you learn "to write / wrote / written" in English. Guessing the prefix is a coin flip; knowing the pair is automatic. The most useful pairs are collected in the aspect pairs overview.

Other prefixes add meaning — they are not aspect partners

Here is the trap behind the trap. A simple verb can take many prefixes, but only one of them is empty. The rest are lexical: they create brand-new verbs with new meanings. Psát alone spawns a whole family, and only napsat is the plain perfective of "to write":

Prefixed verb	Meaning	Empty or lexical?
napsat	to write	empty (aspect partner of psát)
přepsat	to rewrite / retype	lexical (pře- = "re-")
podepsat	to sign	lexical (pod- = "under")
popsat	to describe	lexical
opsat	to copy (off someone)	lexical
vypsat	to fill out / write out	lexical
zapsat	to write down / register	lexical

Each of these is perfective — adding any prefix to an imperfective verb makes it perfective. But only napsat means the same thing as psát. The others are new verbs, and they have their own imperfective partners formed by a suffix (e.g. přepsat → přepisovat), which is the subject of forming imperfectives with suffixes.

Přepsal jsem celý odstavec znovu.

I rewrote the whole paragraph from scratch.

Podepiš se dole na poslední stránce.

Sign at the bottom of the last page.

Zapiš si moje číslo, ať mi můžeš zavolat.

Write down my number so you can call me.

Notice that the same prefix is empty for one verb and lexical for another. Pře- is the empty perfectivizer for číst (přečíst = just "read"), but on psát it is fully lexical (přepsat = "rewrite"). There is no contradiction: prefixes carry meanings, and a meaning happens to come out "empty" only when it adds nothing the base verb didn't already imply. The deeper logic of this split is the whole point of empty vs lexical prefixes.

A reminder about tense

Because the prefixed verb is perfective, it has no present tense. Its present-tense endings carry future meaning. So napíšu does not mean "I write" — it means "I'll write (and finish)." To talk about writing in progress right now, you need the imperfective píšu. This catches every English speaker, so keep it front of mind; the full story is in what verbal aspect is.

Teď píšu e-mail, za chvíli jsem hotová.

I'm writing an email right now, I'll be done in a moment (female speaker).

Večer napíšu ten e-mail a pošlu ti ho.

In the evening I'll write that email and send it to you.

Common Mistakes

❌ Napíšu knihu celý večer.

Incorrect if you mean an ongoing process — napíšu is perfective, so its present form is future ('I'll write and finish'), which clashes with the durative 'all evening'.

✅ Píšu knihu celý večer.

I'm writing a book all evening (process).

❌ Uvařím polévku, právě teď stojím u sporáku.

Incorrect — uvařím is future ('I'll cook'); for cooking in progress use the imperfective vařím.

✅ Vařím polévku, právě teď stojím u sporáku.

I'm cooking soup, I'm standing at the stove right now.

❌ Načetl jsem tu knihu za víkend.

Incorrect — the perfective of číst is přečíst (pře-), not *načíst with na-.

✅ Přečetl jsem tu knihu za víkend.

I read that book over the weekend.

❌ Podepsal jsem ti dlouhý dopis.

Incorrect if you mean 'wrote' — podepsat means 'to sign', not 'to write'.

✅ Napsal jsem ti dlouhý dopis.

I wrote you a long letter.

❌ Budu zavolat doktorovi.

Incorrect — budu never combines with a perfective infinitive; the perfective present is already future.

✅ Zavolám doktorovi.

I'll call the doctor.

Key Takeaways

Prefixing a simple imperfective verb is the commonest way to build its perfective partner: psát → napsat, vařit → uvařit.
One prefix per verb is empty (purely perfectivizing) — it changes the aspect without changing the meaning.
The common perfectivizing prefixes are na-, u-, z-/s-, vy-, po-, pro-, do-, za-, pře-, but you cannot guess which one a given verb takes. Memorize the pair.
Every other prefix is lexical: it creates a new verb (přepsat "rewrite," podepsat "sign"), not just an aspect partner.
The prefixed perfective has no present tense: its present forms (napíšu, uvařím) mean the future.

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