fastball vs slider

fastball and slider both are nouns.

Word	Noun	Adjective	Verb	Adverb
fastball	Yes	No	No	No
slider	Yes	No	No	No

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

fastball: (baseball) a pitch thrown with maximum velocity
slider: a fastball that curves slightly away from the side from which it was thrown

fastball (noun)	slider (noun)
(baseball) a pitch thrown with maximum velocity	a fastball that curves slightly away from the side from which it was thrown
	freshwater turtle of United States and South America; frequently raised commercially; some young sold as pets
	someone who races the luge
	a person who slips or slides because of loss of traction