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Modals of Necessity (Must, Have to, Need to)

Learn how to use must, have to, and need to to express necessity. Understand sentences like I must go vs. I have to go.

What Are Modals of Necessity?

Modals of necessity express that something is required, essential, or obligatory. The most common modals used for necessity are must, have to, and need to.

Why Is This Important?

Using must, have to, and need to correctly helps you indicate the level of necessity or obligation for a certain action.

How to Use 'Must', 'Have to', and 'Need to'

'Must' is used for strong necessity, 'have to' is often used for external obligations, and 'need to' expresses necessity for action.

Common Examples

I must go to the doctor. (Strong necessity)
I have to work tomorrow. (External obligation)
I need to finish this report by 5 PM. (Necessary action)

Key Points

  • Use 'must' for strong personal necessity or obligation
    • I must call my mom.
    • You must wear a helmet when biking.
  • Use 'have to' for external obligations or general necessities
    • I have to go to work tomorrow.
    • She has to submit the report by Friday.
  • Use 'need to' for necessary actions that are required
    • I need to study for the exam.
    • You need to eat more vegetables.

Rules for Using Modals of Necessity

  • Use 'must' for strong personal necessity or internal obligations

    • I must attend the meeting.
    • You must help your brother.
    • She must finish her homework.

  • Use 'have to' for external obligations or general necessity

    • I have to go to the dentist.
    • They have to leave now.
    • He has to make a decision soon.

  • Use 'need to' to express necessity or requirement

    • I need to finish this project today.
    • She needs to apologize for her behavior.
    • We need to buy groceries.

  • Special Cases & Exceptions:

    'Need to' is often used for actions that are required, while 'have to' is typically used for external or imposed obligations.

  • In informal speech, 'have to' is more commonly used than 'must'.

    • Correct: I have to leave now.
    • Incorrect: I must leave now. (In most informal contexts)
ExampleTenseUse
I must go to the doctor.Present'Must' for strong personal necessity
I have to work tomorrow.Present'Have to' for external obligations
I need to finish this report by 5 PM.Present'Need to' for necessary actions
She must submit the assignment by Friday.Present'Must' for strong necessity

Disclaimer: I am not affiliated with the creators of these videos. These are publicly available resources used to provide additional information on the topic.