english grammer world

MUST (Auxiliary Verb)

 (1) Necessary or duty (obligation)
- must indicate that it is necessary that sth happens
- synonym

* need to
* have to
* It is necessary for .... to verb

(ex) I must study English to get a job which have good pay.
= I have to study English to get a job which have good pay.
= It is necessary for me to study English to get a job which have good pay.

 (2) Logical conclusion or logical guess
- must indicate logical conclusions and logical guesses

(a) Events in the present ----- Don't use infinitive

must + be + .... ing
must + be + adjective

(ex) "Her line is busy" "Maybe she must be using the telephone now"
(ex) ASA is not here; She must be sick now.

(b) Events in the past ----- Don't use should, if you use should, the sentence will have different meaning.

must + have + past participle

(ex) Today examination is very difficult; You must have not studied before examination.
(ex) She looks like very sleepy; She must have not slept last night.

(c) Events that repeat ----- Don't use ....ing and infinitive

must + verb word

(ex) Every day Asa is late ; She must go to bed late every night.
(ex) Ken always gets bad point ; She must not study a lot.

 (3) recommending or advising
- If you want to recommend to do something, you can use must

(ex) If you don't understand what teacher say, You must ask teacher.

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modal might modals modal should