Negative imperative

To form a standard negative command, attach the prefix ne- to the imperfective imperative verb (e.g., piš → nepiš). This rule and the aspect shift apply equally to formal/plural forms (-te) and "let's" forms (-me), such as nepište or nekupujme.

Reflexive Verbs
When using reflexive verbs, the negative prefix ne- attaches directly to the verb, not the reflexive pronoun. The pronoun (se or si) typically follows the verb. For example: Neboj se! (Don't be afraid!).

The Aspect Shift
There is a major difference between affirmative and negative commands in Czech. Affirmative commands for single, specific actions use the perfective. However, negative commands default to the imperfective aspect. If the affirmative command you have in mind is perfective, you generally need to "flip" to its imperfective partner for standard prohibitions. Note that this imperfective negative form covers both single-instance prohibitions (don't do it this one time) and general prohibitions (don't do it regularly). If the verb is already imperfective, you simply attach ne-. Highly frequent verbs like být and mít are imperfective, so they simply take ne- (nebuď, neměj). Note that these two verbs have highly irregular imperative stems that cannot be easily derived from the infinitive and simply must be memorized.

• Affirmative: Kup to! (Buy it! - perfective)
• Negative: Nekupuj to! (Don't buy it! - imperfective)

Verbs of Motion
Determinate verbs of motion (like jít and jet) are already imperfective. However, for standard negative commands, they shift to their indeterminate (multidirectional) counterparts (chodit, jezdit). While forms like nejdi and nejeď do exist, they are used specifically to stop or modify an action currently in progress (e.g., Nejdi tak rychle!). Other verbs of motion like běžet or letět do not follow this strict shift; the standard single-instance negative of Běž! is simply Neběž!, while Neběhej! is used for multidirectional or habitual prohibitions.

• Affirmative: Jdi! (Go!) → Standard Negative: Nechoď! (Don't go!)
• Affirmative: Jeď! (Drive/Go!) → Standard Negative: Nejezdi! (Don't drive/go!)

Additionally, the perfective imperative pojď (come) also takes nechoď as its standard negative form, which is a common trap for beginners.

Perfective Negative Imperatives
Many textbooks claim that negative commands always use the imperfective aspect. This is inaccurate. Perfective negative imperatives exist and are used specifically as warnings against accidental slips, involuntary actions, or one-off mistakes.

• Nezapomeň! (Don't forget!)
• Nespadni! (Don't fall!)
• Neztrať to! (Make sure you don't lose it!)

A highly common alternative for expressing these warnings is using ať + the negative present/future tense. This is technically a subordinate clause (short for Dej si pozor, ať... - Watch out so that you don't...), which explains why it uses standard conjugation rather than the imperative form. Native speakers frequently preface this with the word Pozor (e.g., Pozor, ať nespadneš! - Careful you don't fall!, or Ať to neztratíš! - Make sure you don't lose it!).

Third-Person Commands
To form a negative command for the third person (he, she, it, they), use the particle ať followed by the negative present tense verb. For example, Ať to nedělá! (Don't let him do it! / He shouldn't do it!).

Understanding aspectual verb pairs is essential to become confident with this pattern.