What Is Their Main Difference?
Modal Verb Shall
Modal Verb Must
'Must' is a modal verb used to talk about necessities, likely events, and suggestions. Have a look:
Talking about Necessities
We use 'shall' and 'must' to talk about necessities.
- 'Shall' is used to talk about obligations and necessary actions in formal contexts. We often see 'shall' in documents and guidelines. Have a look:
The final product
- 'Must' is also used in less formal contexts to express strong obligation. It refers to both the present and future. For instance:
The final product
Negation and Question
Take a look at these examples:
We can create yes/no questions and wh-questions with modal verbs.
Yes/no questions are made by putting the modal verbs at the beginning of the sentence followed by the subject and the main verb. For example:
With Other Modals
We use only one modal verb in a sentence. We cannot use modal verbs with other modal verbs. Take a look at these incorrect sentences:
shall can pass this test.
must will deny that you saw me with the body.
Formality and Usage
'Shall' and 'must' are both formal when talking about necessities. However, 'shall' is way more formal than 'must,' and since 'shall' is very uncommon, it may sound pretentious and unnatural. Therefore, in normal contexts, we mainly use 'must.'
'Must' is used with conditional type 1. In this type of conditionals, we are talking about a condition and the results that follow. These conditions have a high chance of occurrence. For instance:
If you want to drive the car, you
If he is getting that much money, he
You may hear 'shall' in conditional type 1 statements, but this usage is mainly dedicated to dialects.
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