rest period vs breath

rest period and breath both are nouns.

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

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

Other hyponyms of rest period include breather, breathing place, breathing space, breathing spell, breathing time.

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