Modal Verbs for Ability, Duty, and Necessity

Modal Verbs

• Modal verbs always need to be followed by a base form of a verb (infinitive without to).

Incorrect Usage

• An incorrect usage of a modal verb is when it is used with another modal verb.

Negative Form

• To form the negative form of modal verbs in Simple Present and Simple Past, 'not' is added after the modal verb (e.g., can → cannot, should → should not).

Incorrect Usage in Tenses

• An example of incorrect usage of modal verbs in past or future tenses is when 'will' is used with another modal verb.

'Will' as a Modal Verb

• The special feature of 'will' when used as a modal verb is that it is used to express future actions or events.

Purpose of 'not' with Modal Verbs

• The purpose of using 'not' with modal verbs is to form the negative form.

Modal Verb for Advice

• The modal verb 'must' expresses very strong advice.

'Can' in the Past

• In the past, the modal 'can' changes to 'could'.

Modal Verb for Future Possibility

• The modal verb 'may' is used to show future possibility or to get permission.

Semi-Modal Verb for Necessity

• The semi-modal verb 'have to' shows necessity, obligation, and giving advice.

Modal Verb for Strong Expectation

• The modal verb 'must' is used to express a strong expectation.

Modal Verb with No Tense or Agreement

• The modal verb 'must' does not show tense or subject agreement.

Semi-Modal Verb for Permission

• The semi-modal verb 'be allowed to' is used to show permission.

'Should'

• 'Should' is used to express advice or recommendation.

'Mustn't'

• 'Mustn't' indicates prohibition or something that is not allowed.

'Ought to' and '(Be) supposed to'

• 'Ought to' and '(Be) supposed to' both indicate obligation, duty, or strong advice.