relaxation vs bed rest

relaxation and bed rest both are nouns.

Word	Noun	Adjective	Verb	Adverb
relaxation	Yes	No	No	No
bed rest	Yes	No	No	No

As nouns, bed rest is a hyponym of relaxation; that is, bed rest is a word with a more specific, narrower meaning than relaxation:

relaxation: freedom from activity (work or strain or responsibility)
bed rest: confinement to bed continuously (as in the case of some sick or injured persons)

Other hyponyms of relaxation include bedrest, laziness, lie-in, dormancy, quiescence, quiescency, sleeping, leisure.

relaxation (noun)	bed rest (noun)
freedom from activity (work or strain or responsibility)	confinement to bed continuously (as in the case of some sick or injured persons)
the act of making less strict
a method of solving simultaneous equations by guessing a solution and then reducing the errors that result by successive approximations until all the errors are less than some specified amount
an occurrence of control or strength weakening
a feeling of refreshing tranquility and an absence of tension or worry
(physics) the exponential return of a system to equilibrium after a disturbance
(physiology) the gradual lengthening of inactive muscle or muscle fibers