eupnoea vs breathing

eupnoea and breathing both are nouns.

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

As nouns, breathing is a hypernym of eupnoea; that is, breathing is a word with a broader meaning than eupnoea:

eupnoea: normal relaxed breathing
breathing: the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation

Other hypernyms of eupnoea include external respiration, respiration, ventilation.

eupnoea (noun)	breathing (noun)
normal relaxed breathing	the bodily process of inhalation and exhalation; the process of taking in oxygen from inhaled air and releasing carbon dioxide by exhalation

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