breathless vs dyspneic

breathless and dyspneic both are adjectives.

Word	Noun	Adjective	Verb	Adverb
breathless	No	Yes	No	No
dyspneic	No	Yes	No	No

As adjectives, breathless and dyspneic are synonyms defined as:

breathless and dyspneic: not breathing or able to breathe except with difficulty

Other synonyms of breathless include dyspneal, dyspnoeal, dyspnoeic.

breathless (adjective)	dyspneic (adjective)
not breathing or able to breathe except with difficulty	not breathing or able to breathe except with difficulty
appearing dead; not breathing or having no perceptible pulse
tending to cause suspension of regular breathing