breathing vs breathing in

breathing and breathing in both are nouns.

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

breathing (noun)	breathing in (noun)
the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation	the act of inhaling; the drawing in of air (or other gases) as in breathing

breathing (adjective)	breathing in (adjective)
passing or able to pass air in and out of the lungs normally; sometimes used in combination