subject + must + base verbMust is followed directly by the base verb. Do not use to after must.
Must — Strong Obligation
A2Use must for strong obligation and must not for prohibition. After must, the next verb is always the base form.
What you'll learn
- Use must to express strong necessity or a firm rule.
- Build affirmative sentences with must + base verb.
- Use must not to say something is prohibited.
- Ask yes/no questions with Must + subject + base verb.
- Give short answers with must and must not.
- Recognize words that signal rules, necessity, and prohibition.
Structure
subject + must + not + base verbMust not means prohibition: the action is not allowed.
Must + subject + base verb + ?Put must before the subject. Do not add do or does.
Yes, subject + must. / No, subject + must not.Repeat must in the answer. Do not repeat the main verb.
Build a sentence
Subject
Verb
Youmustwear
You must wear a helmet.
Must makes the rule sound strong.
When to use
Rules
Use must for rules in signs, instructions, and formal notices. Passengers must show ID.
Personal decision
Use must when the speaker feels something is necessary. I must call my mother tonight.
Prohibition
Use must not when something is forbidden. You must not use your phone in the lab.
Markers
necessaryimportantruleallowedforbiddenrequired
In contrast
vs have-to-external-obligation
Must often shows the speaker's strong view or a direct rule. Have to points more to an outside situation or requirement.
Common mistakes
Wrong
You must to wear a seat belt.
Correct
You must wear a seat belt.
After must, use the base verb directly. Do not add to.
Wrong
Maria must arrives by nine.
Correct
Maria must arrive by nine.
Must is followed by the base form, not a present-tense form with -s.
Wrong
You don't must park here.
Correct
You must not park here.
Use must not for prohibition. Do not use do not with must.
Wrong
Do we must leave now?
Correct
Must we leave now?
Questions with must start with must itself, not do.
Common misconceptions
❝ Must not just means something is not necessary. ❞
Must not means prohibition: the action is not allowed. For lack of necessity, English uses do not have to or don't need to.
❝ Must works like want, so it needs to before the next verb. ❞
Must goes directly before the base verb: must go, must stop, must pay.
Skills in this rule (6)
USE_MUST_FOR_STRONG_RULESw5Use must for strong necessity and personal rules
Use must when the speaker sees something as necessary, important, or non-negotiable. It often sounds like a strong instruction, rule, or personal decision.
AFFIRMATIVE_MUST_BASE_VERBw5Build affirmative sentences with must + base verb
After must, use the base form of the main verb. Do not add to or verb endings after must.
NEGATIVE_MUST_NOTw5Use must not for prohibition
Must not means something is not allowed. It is stronger than simple negation and gives a clear prohibition.
QUESTION_MUSTw4Ask questions with Must + subject + base verb
Put must before the subject to make a yes/no question. The main verb stays in the base form.
SHORT_ANSWERS_WITH_MUSTw3Give short answers with must or must not
In short answers, repeat must from the question. Do not add the main verb again.
PICK_OBLIGATION_MARKERSw3Recognize markers of rules and necessity
Words and phrases like rule, necessary, important, and allowed help signal must or must not. They often appear in notices, instructions, and warnings.