The Prefixes s-, z-, and vz-

Few spelling questions trip up learners — and native speakers — as reliably as the choice between the prefixes s- and z-. The trouble is that you cannot hear the difference: before a voiced consonant, s- is pronounced exactly like [z], so sbalit sounds like zbalit. The spelling, though, follows the prefix's meaning and history, not its sound. This page gives you the semantic guideline that resolves most cases, plus the fixed lexical list you have to learn outright. Note this is a different problem from the prepositions s (with) and z (from) — those are separate words, covered elsewhere; here we are dealing with prefixes welded onto verbs.

Why your ears are no help

Czech spelling of these prefixes is etymological: it records where the prefix came from, not how it is pronounced. And pronunciation regularly disguises it through voicing assimilation — a voiceless consonant becomes voiced when a voiced one follows.

In sbalit, the prefix is written s- but pronounced [z] because the following b is voiced. If you spell by sound, you will write zbalit and be wrong. This is precisely why the rule has to be learned visually and by meaning, never by ear.

The semantic guideline

For a large share of verbs, meaning predicts the prefix. Two core meanings dominate:

z- = a change of state, or completion. When the verb describes something becoming different, coming into being, or being finished off, the prefix is usually z-.

Here zlepšit (make better), zničit (make into nothing → destroy), and zmizet (become gone) all encode a transformation. The same logic gives zmrznout (freeze over), zestárnout (grow old), zčervenat (turn red).

s-/se- = together, or down/off. When the verb means motion downward, off a surface, or things coming together, the prefix is usually s-.

Sejít se (come together → meet up), spojit (join together), sundat (take down), smazat (wipe off → delete), sbalit (gather together → pack). The spatial idea — converging, or going down/off — is the thread.

Minimal pairs: the prefix changes the meaning

Because s- and z- carry distinct meanings, a few verb roots produce different verbs depending on which prefix you attach. These pairs are worth studying because they prove the choice is not arbitrary.

Note also zbýt (to be left over) versus zbít (to beat up): same prefix z-, but the roots differ, and so does the spelling of the root vowel. Czech keeps these distinct in writing even though casual speech blurs the boundaries. For the broader picture of how prefixes shift meaning, see prefix meaning shifts and the prefix meanings table.

The must-memorise list

The guideline gets you most of the way, but a stubborn set of common verbs simply have a fixed prefix that you cannot derive from meaning. Learn these as vocabulary.

Always s- (despite the [z] you may hear):

Always z-:

There is no logic that separates skončit (s-) from zkazit (z-) — both begin with the same [sk] cluster, both are voiceless, and both just have to be remembered as they are spelled. Honesty is the kindest teacher here: these are lexical facts, not rules.

vz- = upward or sudden onset

The third prefix, vz-, is much narrower. It signals upward motion or the sudden start of an action, and it is always spelled with both letters.

So vzlétnout (take off, fly up), vzrůst (grow up, increase), vzbudit se (wake up — rouse upward from sleep), vzpomenout si (recall — bring back up to mind). When the sense is "up" or "burst into," vz- is your prefix.

The 1993 reform footnote

A 1993 spelling reform admitted z-spellings for many older loanwords that used to be written only with s, bringing the spelling closer to the pronunciation: kurs → kurz (course), diskuse → diskuze (discussion), renesance → renezance (Renaissance). For most of these the two spellings now coexist as accepted variants; the reference works still treat the s-form as the stylistically neutral base (so renesance and diskuse are the "default" spellings), but the z-form is often what you actually see in everyday writing — kurz and diskuze are now thoroughly mainstream. This affects a set of loanwords, not the verbal-prefix system above, but it explains why you will sometimes see the same word spelled two ways in print.

Common Mistakes

Key Takeaways

• The choice is etymological, not phonetic: before a voiced consonant s- sounds like [z], so you must spell by meaning, not by ear.
• z- = change of state / completion (zlepšit, zničit, zmizet); s-/se- = together or down/off (sejít se, spojit, sundat, sbalit, smazat).
• Minimal pairs prove the system: sbít (nail together) vs zbít (beat up), sjet (go down) vs the others.
• A fixed list must be memorised — always s-: skončit, spojit, schovat; always z-: zkusit, zpívat, zkontrolovat, zlomit.
• vz- is narrow: upward motion or sudden onset (vzlétnout, vzrůst, vzbudit se).