life belt vs constraint

life belt and constraint both are nouns.

Word	Noun	Adjective	Verb	Adverb
life belt	Yes	No	No	No
constraint	Yes	No	No	No

As nouns, constraint is a hypernym of life belt; that is, constraint is a word with a broader meaning than life belt:

life belt: belt attaching you to some object as a restraint in order to prevent you from getting hurt
constraint: a device that retards something's motion

Other hypernyms of life belt include belt, restraint.

life belt (noun)	constraint (noun)
a life preserver in the form of a ring of buoyant material	the act of constraining; the threat or use of force to control the thoughts or behavior of others
belt attaching you to some object as a restraint in order to prevent you from getting hurt	a device that retards something's motion
	the state of being physically constrained