Should vs. Must — What's the Difference?
Edited by Tayyaba Rehman — By Fiza Rafique — Updated on November 1, 2023
"Should" suggests a recommendation or advice, whereas "must" indicates a necessity or obligation.
Difference Between Should and Must
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Key Differences
"Should" and "Must" are modal verbs in English, conveying different degrees of necessity or obligation. "Should" implies a suggestion or recommendation, often expressing what is considered proper or expected. For instance, one should brush their teeth twice a day. "Must," however, communicates an obligation or requirement, often a mandate that has no room for discretion. One must stop at a red traffic light.
While "should" suggests a good or desired action, it carries a sense of optionality. It is used to give advice or to suggest that something is the right thing to do. It does not, however, convey any legal or formal obligation. "Must," on the other hand, is definitive, leaving no choice to the subject. It is used to express compulsory actions, especially those dictated by rules or laws.
In terms of the strength of the modal verbs, "should" is milder and more tentative. It is often used in contexts where the speaker wants to be polite, offering guidance rather than commands. "Must," on the contrary, is strong and direct. It is used in rules, regulations, and situations where compliance is not optional.
The choice between "should" and "must" also affects the tone of a statement. Using "should" can soften the impact, making the statement sound less authoritative, which can be more appropriate in certain social or interpersonal contexts. "Must" can sound strict or uncompromising, which might be necessary in formal or serious situations.
Lastly, "should" can express an expectation or a probable event, particularly when it concerns future events. It is less about obligation and more about what is anticipated to happen. "Must," however, typically refers to a firm necessity in the present or future and can also be used to draw conclusions based on evidence.
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Comparison Chart
Degree of Necessity
Advisable or recommended
Required or obligatory
Imposition
Suggestion, less forceful
Mandate, more forceful
Flexibility
More flexible, allows choice
Less flexible, does not allow choice
Connotation
Advisement with an option to not follow
Compulsion with little or no option to not follow
Use in Formal Obligations
Rarely used to convey legal obligations
Commonly used to convey legal obligations
Compare with Definitions
Should
Used for something that is likely but not certain.
It should rain tomorrow according to the forecast.
Must
Indicates a rule or law must be followed.
Passengers must fasten their seatbelts.
Should
Indicates a lesser degree of obligation.
You should check your email for the update.
Must
Used to deduce a logical conclusion.
If the street is wet, it must have rained.
Should
Expresses an ideal or desired behavior.
We should treat others with kindness.
Must
Must (from the Latin vinum mustum, "young wine") is freshly crushed fruit juice (usually grape juice) that contains the skins, seeds, and stems of the fruit. The solid portion of the must is called pomace and typically makes up 7–23% of the total weight of the must.
Should
Suggests propriety or appropriateness.
You should apologize for your mistake.
Must
To be obliged or required by morality, law, or custom
Citizens must register in order to vote.
Should
Advises on the preferable course of action.
You should wear a helmet while riding a bicycle.
Must
To be compelled, as by a physical necessity or requirement
Plants must have oxygen in order to live.
Should
(auxiliary) Ought to; indicating opinion, advice, or instruction, about what is required or desirable.
Must
Used to express a command or admonition
You must not go there alone. You simply must be careful.
Should
Used to issue an instruction (traditionally seen as carrying less force of authority than alternatives such as 'shall' or 'must').
You should never drink and drive.
The law is clear that you should always wear a seat belt.
The manual says that this switch should be in the 'off' position.
Must
To be determined to; have as a fixed resolve
If you must leave, do it quietly.
Should
Used to give advice or opinion that an action is, or would have been, beneficial or desirable.
You should go and see that film. I think you'll enjoy it.
I should exercise more often, but I’m too lazy.
She should not have been so rude.
Must
Used to indicate inevitability or certainty
We all must die.
Should
(informal) With verbs such as 'see' or 'hear', usually in the second person, used to point out something remarkable in either a good or bad way.
You should see his new apartment. It's like a palace!
If you think her piano playing is bad, you should hear her sing!
Must
Used to indicate logical probability or presumptive certainty
If the lights were on, they must have been at home.
Should
In questions, asks what is correct, proper, desirable, etc.
What do you think? What should I do?
Must
To be required or obliged to go
"I must from hence" (Shakespeare).
Should
(auxiliary) Ought to; expressing expectation.
Must
Something that is absolutely required or indispensable
Promptness on the job is a must. Comfortable boots are a must when going on a hike.
Should
Indicates that something is expected to have happened or to be the case now.
They should have finished by now; I'll call them to check.
My fruit trees should be in flower, but the cold spring has set them back.
Must
The quality or condition of being stale or musty.
Should
Will be likely to (become or do something); indicates a degree of possibility or probability that the stated thing will happen or be true in the future.
They should have it finished by Friday.
When you press this button, the pilot flame should ignite.
You should be warm enough with that coat.
Must
The unfermented or fermenting juice expressed from fruit, especially grapes.
Should
Used to form a variant of the present subjunctive, expressing a state or action that is hypothetical, potential, mandated, etc.
If I should be late, go without me.
Should you need extra blankets, you will find them in the closet.
The man demanded that he should be allowed entry.
I'm surprised that he should say that.
Must
Variant of musth.
Should
(auxiliary) cap=1.
I told him that I should be busy tomorrow.
Must
Musk.
Should
(auxiliary) An alternative to would with first person subjects.
Must
To do with certainty; indicates that the speaker is certain that the subject will have executed the predicate.
If it has rained all day, it must be very wet outside.
You picked one of two, and it wasn't the first: it must have been the second.
Should
Used to express a conditional outcome.
If I had not been so tired, I should have laughed heartily.
Must
To do as a requirement; indicates that the sentence subject is required as an imperative or directive to execute the sentence predicate, with failure to do so resulting in a failure or negative consequence.
Should
Used to impart a tentative, conjectural or polite nuance.
I should imagine that they have arrived by now.
I should think you would apologize.
Must
Used to indicate that something that is very likely, probable, or certain to be true.
The children must be asleep by now.
Should
Used to express what the speaker would do in another person's situation, as a means of giving a suggestion or recommendation.
It's disgraceful the way that they've treated you. I should write and complain.
Must
(transitive) To make musty.
Should
To make a statement of what ought to be true, as opposed to reality. en
Must
(intransitive) To become musty.
Should
Something that ought to be the case as opposed to already being the case.
Must
Something that is mandatory or required.
If you're trekking all day, a map is a must.
Should
Used as an auxiliary verb, to express a conditional or contingent act or state, or as a supposition of an actual fact; also, to express moral obligation (see Shall); e. g.: they should have come last week; if I should go; I should think you could go.
Must
The property of being stale or musty.
Must
Something that exhibits the property of being stale or musty.
Must
Fruit juice that will ferment or has fermented, usually from grapes.
Must
To be obliged; to be necessitated; - expressing either physical or moral necessity; as, a man must eat for nourishment; we must submit to the laws.
Must
To be morally required; to be necessary or essential to a certain quality, character, end, or result; as, he must reconsider the matter; he must have been insane.
Likewise must the deacons be grave.
Morover, he [a bishop] must have a good report of them which are without.
Must
The expressed juice of the grape, or other fruit, before fermentation.
No fermenting must fills . . . the deep vats.
Must
Mustiness.
Must
To make musty; to become musty.
Must
Being in a condition of dangerous frenzy, usually connected with sexual excitement; - said of adult male elephants which become so at irregular intervals, typicaly due to increased testosterone levels.
Must
A necessary or essential thing;
Seat belts are an absolute must
Must
Grape juice before or during fermentation
Must
The quality of smelling or tasting old or stale or mouldy
Must
Highly recommended;
A book that is must reading
Must
Expresses a necessity or obligation.
You must finish your homework before playing.
Must
Implies something is mandatory.
You must stop at a red light.
Must
Suggests a strong recommendation that feels like an obligation.
You must try the cheesecake at this restaurant.
Common Curiosities
Is "must" a stronger directive than "should"?
Yes, "must" indicates a requirement or obligation, stronger than "should."
Are "should" and "must" interchangeable?
No, they are not interchangeable due to differing levels of obligation.
Is it okay to use "should" when giving advice?
Yes, "should" is appropriate for advice.
Does "must" imply legal responsibility?
Often, "must" is used to express compulsory actions, including legal responsibilities.
Is "should" more polite than "must"?
Yes, "should" is generally more polite and less forceful.
Can "must" be used to make a logical conclusion?
Yes, "must" can express a logical deduction.
What does "should" indicate in a sentence?
"Should" indicates a recommendation or advisability.
Can "should" be used to express certainty?
No, "should" implies likelihood or recommendation, not certainty.
Do "should" and "must" have the same modal function?
Both are modals, but their functions differ in terms of obligation and necessity.
Can "should" suggest a probable event?
Yes, "should" can indicate that something is likely to happen.
Can "must" be used to express a strong recommendation?
Yes, "must" can be used for strong recommendations, similar to obligations.
What is the past tense form of "must"?
"Must" doesn't change in the past tense; some use "had to" to convey past necessity.
What is the past tense form of "should"?
"Should" is the same in the past tense.
How do you soften a command using these modals?
Use "should" to soften a command, making it more of a suggestion.
Can "should" be used to express an obligation?
It can imply a moral obligation but is not typically used for formal obligations.
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Written by
Fiza RafiqueFiza Rafique is a skilled content writer at AskDifference.com, where she meticulously refines and enhances written pieces. Drawing from her vast editorial expertise, Fiza ensures clarity, accuracy, and precision in every article. Passionate about language, she continually seeks to elevate the quality of content for readers worldwide.
Edited by
Tayyaba RehmanTayyaba Rehman is a distinguished writer, currently serving as a primary contributor to askdifference.com. As a researcher in semantics and etymology, Tayyaba's passion for the complexity of languages and their distinctions has found a perfect home on the platform. Tayyaba delves into the intricacies of language, distinguishing between commonly confused words and phrases, thereby providing clarity for readers worldwide.
