aerobics vs aerobic exercise

aerobics and aerobic exercise both are nouns.

Word	Noun	Adjective	Verb	Adverb
aerobics	Yes	No	No	No
aerobic exercise	Yes	No	No	No

As nouns, aerobics and aerobic exercise are synonyms defined as:

aerobics and aerobic exercise: exercise that increases the need for oxygen

aerobics (noun)	aerobic exercise (noun)
exercise that increases the need for oxygen	exercise that increases the need for oxygen