Modal Verbs: Have to and Must

Study Notes

Have to:
- Used to express obligation or necessity due to external circumstances
- Often used in formal or professional contexts
- Can be used in present, past, and future tenses
- Examples:
  - I have to attend the meeting tomorrow. (obligation)
  - She had to finish her project last night. (past obligation)
  - They will have to take a taxi if they miss the bus. (future obligation)
Must:
- Used to express strong obligation, necessity, or prohibition
- Often used in formal or official contexts
- Mainly used in present tense, but can be used in past and future tenses with certain constructions
- Examples:
  - You must try this new restaurant. (strong recommendation)
  - By law, you must be 18 to vote. (legal obligation)
  - If you want to succeed, you must work hard. (conditional necessity)

Have to is more commonly used in informal contexts and can imply a sense of reluctance or inconvenience.
Must is often used in more formal or official contexts and implies a stronger sense of obligation or necessity.
Must not is used to express prohibition, whereas don't have to is used to express lack of obligation.

Both have to and must can be used in the negative form to express lack of obligation or necessity.
Have to can be used in questions, while must is typically not used in questions.
Must can be used in passive voice, while have to is not typically used in passive voice.

Have to expresses obligation or necessity due to external circumstances.
It is often used in formal or professional contexts.
Have to can be used in present, past, and future tenses.
Examples of have to:
- I have to attend the meeting tomorrow (obligation).
- She had to finish her project last night (past obligation).
- They will have to take a taxi if they miss the bus (future obligation).

Must expresses strong obligation, necessity, or prohibition.
It is often used in formal or official contexts.
Must is mainly used in the present tense, but can be used in past and future tenses with certain constructions.
Examples of must:
- You must try this new restaurant (strong recommendation).
- By law, you must be 18 to vote (legal obligation).
- If you want to succeed, you must work hard (conditional necessity).

Have to is more informal and can imply reluctance or inconvenience.
Must is more formal and implies a stronger sense of obligation or necessity.
Must not expresses prohibition, while don't have to expresses lack of obligation.

Both have to and must can be used in the negative form to express lack of obligation or necessity.
Have to can be used in questions, but must is not typically used in questions.
Must can be used in passive voice, while have to is not typically used in passive voice.

Have to and Must are used to express obligation, necessity, or strong advice, but have subtle differences in usage and connotation.

Have to implies an external obligation or requirement, often from someone or something else:
- Implies a rule or regulation set by an external authority
- Examples: company policy, deadline set by a teacher
Must implies a stronger sense of obligation or necessity, often from an internal sense of duty or moral imperative:
- Implies a sense of strong recommendation or moral obligation
- Examples: strong advice, moral obligation

Have to expresses a sense of necessity or inevitability:
- Implies a lack of option or alternative
- Examples: task must be done on a specific day, taking a raincoat due to weather
Must expresses a sense of logical necessity or consequence:
- Implies a logical conclusion based on evidence or circumstances
- Examples: studying harder to pass an exam, a cake being delicious based on ingredients