breath vs rest period

breath and rest period both are nouns.

Word	Noun	Adjective	Verb	Adverb
breath	Yes	No	No	No
rest period	Yes	No	No	No

As nouns, rest period is a hypernym of breath; that is, rest period is a word with a broader meaning than breath:

Other hypernyms of breath include relief, respite, rest.

breath (noun)	rest period (noun)
the process of taking in and expelling air during breathing	a pause for relaxation
an indirect suggestion
a slight movement of the air
the air that is inhaled and exhaled in respiration
a short respite