1. Lesson Overview
In this lesson, you will learn:
- How to use should and ought to for advice
- Difference between must and have to
- External vs internal obligation
- How to use need to
- Negative forms and meaning differences
- Semi-modals (have to, need to)
- Common learner errors
These structures express degrees of obligation — from mild advice to strong necessity.
2. Should
A. Form
Subject + should + base verb
She should study harder.
Students should review their notes.
Negative:
She should not (shouldn’t) ignore feedback.
B. Uses
- Advice
You should exercise regularly.
- Recommendation
The report should include references.
- Expectation
The train should arrive soon.
3. Ought To
A. Form
Subject + ought to + base verb
Students ought to respect deadlines.
B. Use
Similar to “should,” slightly more formal or moral tone.
We ought to protect the environment.
Less common in modern spoken English.
4. Must vs Have To
A. Must (Strong Internal Obligation)
I must finish this assignment.
Students must follow the rules.
Often speaker-imposed obligation.
B. Have To (External Obligation)
Subject + have/has to + base verb
She has to wear a uniform.
They have to submit the form by Friday.
Often rule-based or external requirement.
5. Negative Differences
Must not → prohibition
You must not cheat.
Don’t have to → no obligation
You don’t have to attend.
Very important distinction.
6. Need To
A. Form
Subject + need(s) to + base verb
She needs to revise the lesson.
They need to complete the form.
B. Meaning
Expresses necessity, often practical or required for success.
7. Should vs Must vs Have To
|
Modal |
Strength |
|
should |
Advice |
|
ought to |
Moral advice |
|
have to |
External obligation |
|
must |
Strong obligation |
|
need to |
Practical necessity |
8. Common Mistakes Spotlight
⚠ Adding “to” after should
Incorrect: She should to study.
Correct: She should study.
⚠ Confusing must not and don’t have to
Must not = forbidden
Don’t have to = optional
⚠ Incorrect agreement
Incorrect: She have to finish.
Correct: She has to finish.
9. End of Lesson Mastery
You should now be able to:
- Use “should” for advice
- Use “ought to” appropriately
- Distinguish “must” vs “have to”
- Apply “need” correctly
- Understand negative meaning differences