Expressing warnings, commands and prohibitions

This lesson focuses on common expressions used to give warnings, commands (requests or orders), and prohibitions in English. You'll learn typical phrases, tones, and how to choose the right form for different situations—especially in professional contexts.

• Warnings: alert people to a hazard or upcoming issue (e.g., "Warning: Wet floor").
• Commands: ask someone to do something; can be polite requests or direct orders (e.g., "Please submit the report.").
• Prohibitions: forbid actions using negatives or modal verbs (e.g., "Do not enter", "You must not use your phone").

Choose the expression and tone according to urgency and formality:

• Use 'Warning' or 'Caution' on signs and labels to alert people quickly.
• Use the imperative for direct instructions: 'Close the door.'
• Use 'Please' for polite workplace requests: 'Please review the document.'
• Use 'Do not' or 'must not' to make prohibitions clear and unambiguous.

Think: warning = alert, command = action, prohibition = forbid

Learners often make errors that weaken the intended warning, command, or prohibition:

• Using a question form instead of an imperative when a direct instruction is needed (e.g., 'Could you close the door?' vs 'Close the door.').
• Omitting negative words in prohibitions (e.g., saying 'Enter the area' instead of 'Do not enter the area').
• Mixing levels of politeness incorrectly — sounding too informal or too harsh for a professional context.
• Using weak modal verbs that reduce force when a strong prohibition is required (e.g., 'should not' instead of 'must not' when a rule is mandatory).

Check tone, verb form, and negative words to make your message clear.