athletics vs riding

athletics and riding both are nouns.

Word	Noun	Adjective	Verb	Adverb
athletics	Yes	No	No	No
riding	Yes	No	No	No

As nouns, riding is a hyponym of athletics; that is, riding is a word with a more specific, narrower meaning than athletics:

athletics: an active diversion requiring physical exertion and competition
riding: the sport of sitting on the back of a horse while controlling its movements

athletics (noun)	riding (noun)
an active diversion requiring physical exertion and competition	travel by being carried on horseback
participation in sports events as an extracurricular activity	the sport of sitting on the back of a horse while controlling its movements
a contest between athletes