Difference Between Shall and Must

Introduction

Rules can prove to be quite the dampers on a party. Granted, not everybody thinks them so. Some people are just sticklers for rules. They revere rules. Quite like Hermoine Granger from Harry Potter. And then there are the polar opposite ones or the naughty ones. They hate rules. They seek to break them as if it is their lives’ mission. For them, breaking rules is a sacred duty. Most other people fall in between these polar groups. As a student, certainly, you’ve broken a rule or two. And certainly, breaking those rules did not endanger lives (you are reading this article, after all). Breaking or even bending a few rules are almost considered a rite of passage of youth. 

While breaking a few rules might be harmless, the objective of their existence is rather important. Rules, as one grows up to learn, are what govern a society. They are essential and shape the community. Rules are a way to ensure the general safety of individuals and protect our rights against abusers be it other people or even the government itself. They serve to guide us towards appropriate action in any situation be it driving only when the light turns green or reporting to the officials about the man with a bloody knife. They might be hard to follow, you might just be tempted to jaywalk on a bright day, but rules are your life jacket.

Shall vs. Must

Often, rules aren’t optional. They are definitive and final. To make them seem so, the sentences usually use the words – shall and must. Both of these words ensure that the action is to be committed. But, they cannot quite be used interchangeably. Let us see how each of them shapes the rules differently.

Differences Between Shall and Must in a Tabular Form

PARAMETER	SHALL	MUST
Definition	‘Shall’ is a modal verb used to express a need or an obligation.	‘Must’ is also a modal verb used to express a need or an obligation but it has a stronger intent.
Purpose	‘Shall’ is employed in sentences that demonstrate a willingness, intention, suggestion or insistence.	‘Must’ is employed in sentences that demonstrate a necessity, compulsion, deduction, certainty or probability.
Derivation	‘Shall’ originated in the 17th century, with the ground sense of the word in Germanic being ‘I owe’ or ‘I ought’.	‘Must’ originated in the 12th century, the meaning of the word derived from Old English ‘moste’ meaning to ‘be obliged or impelled’.
Grammatical use	‘Shall’ is used as a modal verb along with the base form of the verb. Most commonly, ‘shall’ is used with the pronouns ‘I’ and ‘we’.	‘Must’ is also a modal verb. In a verb phrase, it comes first i.e. after the subject and before the verb.
Tense	‘Shall’ is used for future time reference.	‘Must’ can be used to give a present or a future reference.
Common use	‘Shall’ is more commonly used in formal situations.	‘Must’ is more commonly used informally or in legal situations.
Legal use	‘Shall’ is not favoured since it expresses vagueness.	‘Must’ is favoured since it is clearer to express requirement.
Contraction	‘ll is generally the contraction of ‘shall’ but is more often used as a contraction of ‘will’.	‘Must’ does not have a contraction.
Negative contraction	The negative contracted form of ‘shall not’ is ‘shan’t’	The negative contracted form of ‘must not’ is ‘mustn’t’
Example	I shall bake the cake for your birthday.	You must bring the book to room.

When do we use Shall?

‘Shall’ is a modal auxiliary verb. These kinds of verbs are also known as helping verbs. They help add meaning to the verb in a sentence. ‘Shall’ is used with the base form of the main verb of any sentence. It is also used in the future reference of time and formal settings. Most often, it appears with the pronouns ‘I’ and ‘we’. In the law enforcement departments, the use of ‘shall’ is frowned upon. It is considered vague and ambiguous and its use is advised against.

Examples of the use of ‘Shall’ in sentences along with their uses:

• As a prediction:

‘Shall’ can be used when making predictions or even stating facts about the future. For example:

We shall need more snacks when the kids arrive.

• As decisions and offers:

‘Shall’ can be used when announcing decisions or making offers or suggestions. For example:

I shall be in touch about the vacancy.

Shall I invite the neighbours to the party?

• Use of ‘Shall’ with ‘I’ and ‘we’:

Using ‘shall’ with ‘I’ and ‘we’, makes the sentence more formal. For example:

I shall always remember the lessons taught by her.

• As obligations in official documents:

‘Shall’ is used in documents for formal obligations. For example:

Employees shall wear their ID badges at all times in the office.

• In an affirmative sentence:

Here is an example of a sentence with ‘shall’ and a first-person pronoun.

I shall receive the guests at noon.

Following is an example of the use of ‘shall’ with second-person and third-person pronouns. In such cases, ‘shall’ is used to emphasize the verb.

You shall sing with all your heart.

They shall attend the wedding even if it rains.

• In a negative sentence:

Following is an example of ‘shall’ in a negative sentence.

I shall not entertain those mischievous children.

In the same sentence, using the contraction, ‘shan’t’

I shan’t entertain those mischievous children.

• In an interrogative sentence:

‘Shall’ can also be used to pose questions. Such questions are mostly requests or suggestions. For example:

Shall we make way for the parade?

Shall we go dancing tonight?

When do we use Must?

‘Must’ is also an auxiliary modal verb. It is also used as a verb for obligation, necessity or requirement but it is used only when a person is sure of their intention. It is a stronger word. While ‘shall’ offers an option of doing or not doing an action, ‘must’ demands that the action be performed. It is rather a basic way of saying that something is compulsory. ‘Must’ can only be used in the present form to say that an action has to be performed at that instant or in the future.

In a verbal phrase, ‘must’ comes after the subject and before the verb, for example:

I must go. (subject – I; verb – go)

In the legal jargon, ‘must’ is recommended to be used while talking of requirements and prohibitions since it is considered more imperative. The use of ‘must’ along with ‘shall’ is not a good practice for the drafters since it could mean two different things.

Examples of the use of ‘Must’ in sentences along with their uses:

• As an obligation:

All students must bring their lunch boxes to school.

• As orders:

‘Must’ can be used to give firm orders. For example:

You must go to bed on time.

• As orders or pieces of advice:

‘Must’ can be used to give orders or to make recommendations. For example:

You must read that textbook; it is very insightful.

You must buy that hat; it is lovely.

• To make speculations:

‘Must’ is also used while guessing about the state of things. For example:

You must be kidding!

He must be crazy to buy that car!

• With a past participle:

‘Must’ can be used with a past participle (verbs indicative of the past incident; mostly end with -ed). At such times, ‘must’ is followed by ‘have’. For example:

She must have missed the turn. (past participle – missed)

He must have found the ring. (past participle – found)

• In an affirmative sentence:

I must get home before the rain starts to pour.

• In a negative sentence:

Following is an example of ‘must’ in a negative sentence. It usually signifies prohibition.

You must not let the dogs jump on the bed.

In the same sentence, using the contraction, ‘mustn’t’

You mustn’t let the dogs on the bed.

• In an interrogative sentence:

‘Must’ can also be used in questions but it is not very common in Modern English. For example:

Must we invite her to the wedding?

Must you leave tomorrow?

Differences Between Shall and Must in Points

Following are the main differences between the use of Shall and Must:

1. ‘Shall’ originated in the 17^th century and is derived from Germanic words meaning ‘I owe’ or ‘I ought’. ‘Must’ originated much earlier, in the 12^th century and is derived from the Old English word ‘moste’ which means, to ‘be obliged or impelled’.
2. ‘Shall’ is used in sentences that wish to express an obligation or need whereas ‘must’ is used in sentences that wish to express compulsion, deduction, necessity or a probability.
3. ‘Shall’ is a modal verb used along with the base verb form. It is more commonly used with the pronouns – ‘I’ and ‘we’. ‘Must’ is also a modal verb. It is used in such a way that in a verb phrase it comes after the subject and before the verb.
4. ‘Shall’ is found to be more formal while ‘must’ can be used informally.
5. In the legal language, ‘shall’ is not preferred to be used since it is rather vague. ‘Must’, on the other hand, is favoured since it depicts clarity of requirement.
6. ‘Shall’ is used in the future time reference whereas ‘must’ is used for a present or future time reference.
7. ‘ll is generally the contraction of ‘shall’ but is more often used as a contraction of ‘will’. ‘Must’ does not have a contraction. The negative contracted form of ‘shall not’ is ‘shan’t’ and the negative contracted form of ‘must not’ is ‘mustn’t’.
8. An example of a sentence with ‘shall’ is as follows – ‘I shall wear this badge with honour’. An example of a sentence with ‘must’ is as follows – ‘He must train harder to win the marathon.’

Conclusion

‘Shall’ and ‘must’ are thus both modal auxiliary verbs that are used to convey an obligation or a need. ‘Shall’, however, is used in a more formal setting. It is more commonly used with first-person pronouns like ‘I’ and ‘we’. Although, it can be used with second-person and third-person pronouns as well. When such a scenario occurs, ‘shall’ brings more emphasis to the verb in the sentence. ‘Shall’ is used for reference to the future. Since it offers an option to the listener, it is considered more demure in contrast to ‘must’. It is also considered ambiguous and is avoided in legal arguments.

‘Must’ is a more definitive verb. It is most often used in sentences that need to convey a compulsion or a necessity. It can be used informally as well as formally and is more prevalent in normal conversation when compared to ‘shall’. It can be used to give a present or a future reference. Since it is more definitive and clear, it is favoured for use in legal arguments and documents. However, it is important to note that both ‘shall’ and ‘must’ should not be used together in a legal document since they could mean two different things and lead to a misunderstanding.

Since both ‘shall’ and ‘must’ depict requests and orders, they are most likely to be found in the rules that tempt us so. Rules like – ‘you mustn’t bring your phone to a lecture’ or ‘they shall walk in a straight line’, truly couldn’t kill you if you broke them. But rules like – ‘you mustn’t lean against the railing’ or ‘thou shalt not kill’ (‘shalt’ is the ancient form of ‘shall’), could kill you. Or drag you to prison. Either way, following rules is only safer and keeps one out of trouble. The gallows are surely worse than the comfort of your sofa, not to forget the ever-loving family that depends on you. They might be the reason you seek out the trouble but surely, they can’t be that bad. Perhaps, you should come up with a rule book for them. You even know now what modal verbs to use. A family rule book full of rules made by you for their benefit. And yours.

References

1. https://www.etymonline.com/word/shall
2. https://www.etymonline.com/word/must
3. https://grammar.collinsdictionary.com/easy-learning/when-do-you-use-must-in-english
4. https://dictionary.cambridge.org/grammar/british-grammar/future-will-and-shall
5. https://www.bespeaking.com/modal-verbs-part2/
6. https://grammar.collinsdictionary.com/easy-learning/when-do-you-use-must-in-english
7. https://www.plainlanguage.gov/guidelines/conversational/shall-and-must/
8. https://www.wallstreetenglish.com/exercises/the-difference-between-must-have-to-shall-need-and-may