Obligation and permission

Modal verbs are important for expressing obligation and permission in English.

Here is a summary of some common modal verbs and phrases that are used to express obligation and permission:

Modal Verb/Phrase	Meaning	Example	Grammar Pattern
needn’t	no obligation	You needn’t come to the party if you don’t want to.	need not + base verb
must	strong obligation	I must finish this report by tomorrow.	must + base verb
ought to	strong recommendation (very formal)	You ought to apologize for your behavior.	ought to + base verb
should	advice/suggestion/ weak obligation	I should study for the exam.	should + base verb
can	permission	Can I use your pen, please?	can + base verb
be required	necessary	A valid passport is required to enter the country.	be + required to + base verb
be not required	not necessary	A tie is not required for the interview.	be + not required to + base verb
be allowed	permission	You are allowed to smoke in this area.	be + allowed to + base verb
be not allowed	prohibition	You are not allowed to smoke in this area.	be + not allowed to + base form
be supposed to	expectation/ weak obligation	We are supposed to arrive at 8:00 AM.	be + supposed to + base verb
be not supposed to	not allowed	You are not supposed to use your phone in class.	be + not supposed to + base verb
it’s illegal to	against the law	It’s illegal to park here.	it’s illegal to + base verb
it’s against the law	against the law	It’s against the law to steal.	it’s against the law to + base verb
it’s polite	socially acceptable	It’s polite to say “please” and “thank you”.	it’s polite to + base verb
it’s impolite	socially unacceptable	It’s impolite to interrupt someone.	it’s impolite to + base verb
it’s best to	advice/suggestion (positive)	It’s best to arrive early for your interview.	it’s best to + base verb
it’s best not to	advice/suggestion (negative)	It’s best not to eat too much junk food.	it’s best not to + base verb