must
A1Formal and informal; universally common.
Definition
Meaning
Used to express necessity or strong obligation, often from an external rule or law.
Used to express logical certainty or a strong recommendation based on the speaker's opinion.
Linguistics
Semantic Notes
"Must" is a modal auxiliary verb. It lacks infinitives, participles, and past forms. For past obligation, "had to" is used. For negative obligation (prohibition), "must not" (mustn't) is used. For absence of necessity, "don't have to" or "needn't" is used, not "mustn't".
Dialectal Variation
British vs American Usage
Differences
In British English, "mustn't" is common for prohibition. In American English, "can't" or "may not" are often preferred in speech. British English more readily uses "must" for internal obligation (e.g., "I must say").
Connotations
In both, "must" can sound authoritative or impatient. In British English, it may carry a slightly more formal or institutional tone.
Frequency
Slightly higher frequency in British English, especially in written rules and advisories. Americans may use "have to" or "need to" more often in casual speech for personal obligation.
Vocabulary
Collocations
Grammar
Valency Patterns
must + base form of verb (e.g., must go)must + be + present participle (e.g., must be joking)must + have + past participle (e.g., must have forgotten)Vocabulary
Synonyms
Strong
Neutral
Weak
Vocabulary
Antonyms
Phrases
Idioms & Phrases
- “A must-see”
- “A must-have”
- “Must needs (archaic)”
Usage
Context Usage
Business
Used in contracts, policies, and directives to denote mandatory requirements (e.g., 'The report must be filed quarterly').
Academic
Used to express logical deduction in arguments (e.g., 'These findings must challenge the existing theory').
Everyday
Used for personal obligations, strong recommendations, or deductions (e.g., 'You must try this cake!', 'He must be at home by now').
Technical
Used in specifications, manuals, and safety protocols to indicate compulsory procedures (e.g., 'The system must be grounded before service').
Examples
By Part of Speech
verb
British English
- All passengers must present their tickets.
- One must consider the environmental impact.
- This must be the right address.
American English
- You must have a permit to park here.
- I must disagree with that assessment.
- She must have left her phone at the office.
adverb
British English
- This is must-watch television.
- The film is a must-see event.
American English
- The app is a must-download for musicians.
- His latest book is a must-read.
adjective
British English
- This new thriller is a must for film fans.
- A waterproof jacket is a must for hiking in Scotland.
American English
- Visiting the Grand Canyon is a must-do.
- A good internet connection is a must for remote work.
Examples
By CEFR Level
- You must stop at a red light.
- I must go to the supermarket.
- She must be his sister, they look alike.
- Students must hand in their essays by Friday.
- You must be joking! That can't be true.
- It's getting late; I really must be going.
- Candidates must demonstrate at least five years of relevant experience.
- Given the market volatility, investors must proceed with caution.
- He must have taken the later train; he's not here yet.
- The prosecution must prove guilt beyond a reasonable doubt.
- Any credible theory of change must account for these socioeconomic factors.
- They must have been waiting for hours in this dreadful weather.
Learning
Memory Aids
Mnemonic
Think of a dusty, ancient law scroll with the words 'YOU MUST...' stamped in red. It combines necessity (MUST get it done) and certainty (it MUST be true).
Conceptual Metaphor
OBLIGATION IS A PHYSICAL FORCE (must = being pushed). CERTAINTY IS A SOLID OBJECT (must = it is solidly true).
Watch out
Common Pitfalls
Translation Traps (for Russian speakers)
- Confusing "must" with "должен". "Должен" can imply moral duty, while "must" often implies external rule. "I must go" = меня вынуждают обстоятельства, not just я должен.
- Using "must" for past obligation. Use "had to" (пришлось). "I must do it yesterday" is incorrect.
- Using "mustn't" to mean "not necessary". Use "don't have to" (не нужно, не обязательно).
Common Mistakes
- *I must to go. (Correct: I must go.)
- *He musts go. (Correct: He must go.)
- *You must not be tired. (To mean 'It's not necessary for you to be tired' is incorrect. Use 'You don't have to be tired.')
- *I must call him yesterday. (Correct: I had to call him yesterday.)
Practice
Quiz
Which sentence correctly expresses a logical deduction about the past?
FAQ
Frequently Asked Questions
'Must' often implies the obligation comes from the speaker's authority or internal feeling. 'Have to' often implies an external rule or circumstance. In practice, they are often interchangeable, especially for strong obligation.
You use 'had to'. For example, 'Yesterday, I had to finish my report.' There is no past form of 'must' itself.
No. 'Mustn't' means it is forbidden (нельзя). 'Don't have to' means it is not necessary (не нужно). Example: 'You mustn't smoke here' (it's prohibited). 'You don't have to pay' (it's free, but you can if you want).
Yes, but it's strong, emphatic advice, closer to a recommendation you feel very strongly about. For softer advice, use 'should' or 'ought to'. Example: 'You must visit the British Museum when you're in London!'
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