breathing out vs expiration

breathing out and expiration both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathing out	Yes	No	No	No
expiration	Yes	No	No	No

As nouns, breathing out and expiration are synonyms defined as:

Other synonyms of breathing out include exhalation.

breathing out (noun)	expiration (noun)
the act of expelling air from the lungs	the act of expelling air from the lungs
	euphemistic expressions for death
	a coming to an end of a contract period