Forming Imperfectives with Suffixes

You already know one way Czech builds an aspect pair: stick a prefix on a simple imperfective verb to make its perfective partner (psát → napsat). This page is the mirror image, and it solves a problem the prefix method creates. When a prefix does more than just perfectivize — when it adds meaning and produces a new lexical verb like podepsat "to sign" or přepsat "to rewrite" — that new verb is perfective and has no imperfective. Czech needs to give it one. It does so not with another prefix but with a suffix, typically -ovat, -ávat, or -vat, inserted into the verb. This process is called secondary imperfectivization, and it is the engine that keeps an imperfective partner available for the hundreds of meaning-bearing prefixed verbs in the language.

The problem the suffix solves

Start from a base imperfective. Add an empty prefix and you get its plain perfective — done, no suffix needed. But add a meaning-adding prefix and you have a brand-new perfective verb stranded without an imperfective. The suffix builds that missing partner.

The result is often a three-way relationship worth seeing clearly. Psát is the plain base imperfective ("to write, in general"). Podepsat is a perfective with extra meaning ("to sign"). And podepisovat is the secondary imperfective that restores the imperfective option for that new "sign" meaning. Three verbs, two aspects, one root.

The three suffixes

The work is done by one of three closely related suffixes. They are not freely interchangeable — each verb takes a particular one — but the families are learnable.

-ovat (the workhorse)

By far the most productive. It attaches to a huge range of perfectives, very often turning a final consonant and inserting -ova-:

-ávat

Builds imperfectives that frequently carry an extra iterative / habitual flavor — the action done repeatedly or as a custom, not just generically. It often pairs with the dát-type roots and with verbs of giving, asking, putting:

-vat

A lighter variant that attaches after a vowel, common with -it perfectives whose stem ends in a vowel:

The stem and vowel changes that come along

The suffix rarely attaches cleanly — it usually triggers a predictable change in the stem, most often a vowel shortening or a consonant softening. This is the part learners find fiddly, so it pays to see the pattern rather than memorize each form cold.

The classic example is koupit → kupovat: the long ou of the perfective shortens to u in the imperfective, and -ovat is added. That vowel-shortening reflex (á → a, í → i, ou → u) shows up again and again, so train your ear to expect a shorter vowel in the imperfective.

Why English has nothing like this

English handles "completed vs ongoing" with separate words or with the progressive (write / be writing) and conveys "rewrite, sign, explain" with prefixes and separate verbs — but it never runs the two systems together. Czech does. It first uses a prefix to create a meaning (and incidentally perfectivize), then uses a suffix to restore the aspect choice for that new meaning. So a single English verb like "to sign" corresponds to a Czech pair — podepsat (pf.) and podepisovat (impf.) — and you must pick the member that matches whether the signing is one completed act or a habitual/ongoing one. There is no English instinct that does this for you; it is bookkeeping you take on when you learn the verb.

Common Mistakes

Key Takeaways

• A meaning-adding prefix creates a new perfective verb with no imperfective; Czech supplies one by secondary imperfectivization — adding a suffix.
• The suffixes are -ovat (most productive), -ávat (often iterative/habitual), and -vat (after vowels).
• This yields a three-way set: base imperfective (psát), prefixed perfective (podepsat), secondary imperfective (podepisovat).
• The suffix usually triggers a vowel shortening (koupit → kupovat) or consonant change (vrátit → vracet) — expect a shorter vowel in the imperfective.
• English has no equivalent: one English verb like "sign" maps onto a Czech perfective/imperfective pair you must choose between.