Meaning of “law” - Learner’s Dictionary

law

noun uk us /lɔː/
the law

B2 the system of official rules in a country:

You're breaking the law.
It's against the law (= illegal) not to wear seat belts.
It's their job to enforce the law.
by law

B2 If you have to do something by law, it is illegal not to do it:

They have to provide a contract by law.
RULE [ C ]

B2 an official rule in a country:

There are laws against drinking in the street.
They led the fight to impose laws on smoking.
law and order

the obeying of laws in society:

a breakdown in law and order
SUBJECT [ U ]

B1 the subject or job of understanding and dealing with the official laws of a country:

a law school/firm
ALWAYS TRUE [ C ]

something that is always true in science, mathematics, etc.:

the laws of nature/physics
the law of averages/gravity
→ See also brother-in-law , common-law , daughter-in-law , father-in-law , in-laws , martial law , mother-in-law , sister-in-law , son-in-law , lay down the law

(Definition of “law” from the Cambridge Learner’s Dictionary © Cambridge University Press)