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Modal Verbs: Obligation, necessity and permission.

Must and musn´t Strong Obligation

Must and musn´t Must *Affirmative form: Subject +must + verb (inf) + complement Examples: - You must go - You must visit us soon

Mustn´t *Negative form: subject + mustn´t + verb (inf) + complement Examples: - You mustn´t go to that meeting. -We musn´t be late

Interrogative form Must + subject + verb (inf) + complement? Examples: - Must you live now? - Must you travel to Barcelona tomorrow?

Must and mustn´t � Must is used to talk about strong obligations in the present and future that are imposed by the speaker. � The negative form of "must" expresses the idea that something is prohibitied.

Should, Shouldn't and Ought to Weak Obligation.

Should and Shouldn't Should


*Affirmative form: Subject + should + verb (inf) + complement

*Negative form: subject + shouldn't + verb (inf) + complement

Examples: - (You look tired) You should take a nap. - I should study for tomorrow's test.

Examples: - You shouldn't run in the hallways - You shouldn't have talk to him like that.

Interrogative form Should + subject + verb (inf) + complement? Examples: - Should I talk to him? -Yes, you should -No, you shouldn't

- Should I tell Mary about it? - Yes, you should - No you shouldn't

Should and Shouldn't ● Give suggestion on what is the right thing for somebody to do. ● Give advise or talk about what we think is right or wrong. ● Make orders and instructions more polite

Ought to *Affirmative form: Subject + ought to + verb (inf) + complement Example: -You ought to drive carefully -You ought to clean your room before you leave. *Hardly ever used in negative form: Subject + ought not/oughtn't to + verb (inf) + complement Example: -We ought not/oughtn't to have agreed without knowing what it would cost. *NOT USED in interrogative form.

Differences Ought to


● You suggest someone what is one of the last options one has or something that one can't easily avoid, for example, any longer.

● You suggest someone that something is good to be done or something that after all is meaningful.

● It is more explicit, similiar to a request.

● It is not as explicit as ought to.

Example: -You ought to tell her how you feel. (You can't avoid telling her how you feel)

Example: - You should tell her how you feel. (It is better or the best to tell her how you feel)

Let's practice! Create 3 sentences using "should" and "shouldn't"

Create 3 sentences using "ought to"


Create 3 sentences using "must and mustn´t -


The modals are: should, shouldn´t, ought to, must and musn´t