constraint vs air bag

constraint and air bag both are nouns.

Word	Noun	Adjective	Verb	Adverb
constraint	Yes	No	No	No
air bag	Yes	No	No	No

As nouns, air bag is a hyponym of constraint; that is, air bag is a word with a more specific, narrower meaning than constraint:

constraint: a device that retards something's motion
air bag: a safety restraint in an automobile; the bag inflates on collision and prevents the driver or passenger from being thrown forward

constraint (noun)	air bag (noun)
the act of constraining; the threat or use of force to control the thoughts or behavior of others	a safety restraint in an automobile; the bag inflates on collision and prevents the driver or passenger from being thrown forward
a device that retards something's motion
the state of being physically constrained