must not be

USAGE SUMMARY

"must not be" is correct and can be used in written English.
It is generally used to indicate something that is not allowed or forbidden. For example, "Drivers must not be on their phones while driving."

✓ Grammatically correct

News & Media

Science

Formal & Business

Wiki

Human-verified examples from authoritative sources

Exact Expressions

60 human-written examples

This must not be allowed.

The New York Times

We must not be enemies.

Forbes

Women must not be separated.

Independent

It must not be forgotten.

The New York Times

This must not be forgotten.

Independent

"Actors must not be boring.

The New York Times - Books

It must not be there.

The New Yorker

It must not be glacial.

The Economist

He must not be.

The Guardian - Opinion

This must not be allowed to happen.

The Guardian

They must not be taken for granted.

The New York Times

Expert writing Tips

Best practice

When employing "must not be" in formal writing, maintain a consistent tone of authority and clarity. In more casual contexts, consider softer alternatives like "should not be".

Common error

Avoid using "must not be" in casual conversation or informal writing where a less forceful expression would be more appropriate. Overusing strong prohibitions can sound overly authoritarian or stilted.

Linguistic Context

The phrase "must not be" functions as a modal verb phrase expressing prohibition, obligation, or strong necessity. It indicates that something is forbidden or highly undesirable. Ludwig AI confirms this through numerous examples across various domains.

Expression frequency: Very common

Frequent in

News & Media

50%

Science

15%

Formal & Business

15%

Less common in

Wiki

5%

Encyclopedias

0%

Reference

0%

Ludwig's WRAP-UP

In summary, "must not be" is a modal verb phrase used to express strong prohibition, necessity, or obligation. Ludwig AI indicates that it's grammatically correct and frequently used, particularly in news, science, and formal business contexts. While versatile, it's essential to consider the tone, avoiding overuse in informal settings to maintain an appropriate level of formality. Remember to use softer alternatives like ""should not be"" or ""cannot be"" when a less forceful expression is suitable.

More alternative expressions

Phrases that express similar concepts, ordered by semantic similarity:

absolutely must not be

Adds emphasis to the prohibition.

must never be

Emphasizes the perpetuity of the prohibition.

should not be

Replaces 'must' with 'should', softening the prohibition.

cannot be

Indicates impossibility rather than prohibition.

is not allowed to be

Formal and explicit prohibition.

is forbidden to be

Stronger and more formal prohibition.

is not permitted to be

Similar to 'is not allowed', but slightly more formal.

is prohibited from being

Emphasizes the act of prohibiting.

ought not to be

Expresses a moral obligation not to be.

is essential not to be

Highlights the importance of avoiding a particular state.

FAQs

How to use "must not be" in a sentence?

Use "must not be" to express a strong prohibition or necessity. For example, "The evidence "must not be" tampered with".

What can I say instead of "must not be"?

You can use alternatives like "should not be", "cannot be", or "is not allowed to be" depending on the level of formality and strength of the prohibition.

Which is correct, "must not be" or "must be not"?

"Must not be" is the correct and standard form. "Must be not" is grammatically incorrect and rarely used.

What's the difference between "must not be" and "should not be"?

"Must not be" indicates a stronger prohibition or necessity than "should not be". "Must not be" implies a rule or strict requirement, while "should not be" suggests a recommendation or advice.