breathing in vs inhalation

breathing in and inhalation both are nouns.

Word	Noun	Adjective	Verb	Adverb
breathing in	Yes	No	No	No
inhalation	Yes	No	No	No

As nouns, breathing in and inhalation are synonyms defined as:

breathing in and inhalation: the act of inhaling; the drawing in of air (or other gases) as in breathing

Other synonyms of breathing in include aspiration, inspiration, intake.

breathing in (noun)	inhalation (noun)
the act of inhaling; the drawing in of air (or other gases) as in breathing	the act of inhaling; the drawing in of air (or other gases) as in breathing
	a medication to be taken by inhaling it