law vs common-law marriage

law and common-law marriage both are nouns.

Word	Noun	Adjective	Verb	Adverb
law	Yes	No	No	No
common-law marriage	Yes	No	No	No

law (noun)	common-law marriage (noun)
the learned profession that is mastered by graduate study in a law school and that is responsible for the judicial system	a marriage relationship created by agreement and cohabitation rather than by ceremony
a rule or body of rules of conduct inherent in human nature and essential to or binding upon human society
a generalization that describes recurring facts or events in nature
the branch of philosophy concerned with the law and the principles that lead courts to make the decisions they do
legal document setting forth rules governing a particular kind of activity
the collection of rules imposed by authority
the force of policemen and officers