"must not" vs "must'nt"

Question

"must not" vs "must'nt"

Both "must not" and "mustn't" are correct contractions of "must not." However, "must not" is more formal and commonly used in written and spoken English, while "mustn't" is more informal and often used in casual conversations.

Last Updated: March 21, 2024

Use "must not" to indicate prohibition or to give a strong recommendation. It is more formal and suitable for both written and spoken English.

Examples:

You must not enter this area.
She must not forget to bring her ID.
We must not underestimate the importance of this decision.

Alternatives:

should not
cannot
may not
ought not
shall not

Use "mustn't" in informal spoken English to indicate prohibition or strong recommendations. It is more casual and suitable for everyday conversations.

Examples:

You mustn't forget to call your mom.
He mustn't be late for the meeting.
We mustn't tell anyone about the surprise party.

Alternatives:

shouldn't
can't
mayn't
oughtn't
shan't

Answer 1

must not

This is a correct and commonly used phrase in English.

Answer 2

must'nt

This is a correct contraction of "must not" but is more informal and less commonly used in formal contexts.

"must not" vs "must'nt"

must not

must'nt

Related Comparisons