|Modals||Must||Have to||Need to|
|Uses||Expressing strong obligation (positive/negative), expressing rules (positive/negative).||Expressing obligation, asking about obligations (positive), expressing optional actions (negative).||Expressing obligation (positive/negative), asking about obligations (positive)|
|Formality||Formal||Formal / Informal||Informal|
|Examples||Expressing strong obligation (positive):|
You must pay your taxes.
Expressing strong obligation (negative):
You must not leave before the meeting ends.
You mustn’t tell the boss about this.
Expressing rules (positive):
Employees must wash their hands.
Expressing rules (negative):
Employees must not wear hats indoors.
NOTE- The contraction (mustn’t) is rarely used when talking about rules.
You have to give me the report by noon.
Asking about obligations:
Do I have to print the entire document?
Expressing optional actions:
You do not have to work today. (You can, but it isn’t required).
|Expressing obligation (positive):|
You need to take your time.
Expressing obligation (negative):
You don’t need to rush.
Asking about obligations (positive):
Do I need to email you?