ball vs crystal ball

ball and crystal ball both are nouns.

Word	Noun	Adjective	Verb	Adverb
ball	Yes	No	Yes	No
crystal ball	Yes	No	No	No

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

ball: an object with a spherical shape
crystal ball: a glass or crystal globe used in crystal gazing by fortunetellers

Other hyponyms of ball include camphor ball, mothball, time-ball, fireball, fireball, globule, spherule, pellet, bolus.

ball (noun)	crystal ball (noun)
a pitch that is not in the strike zone	a glass or crystal globe used in crystal gazing by fortunetellers
a ball game played with a bat and ball between two teams of nine players; teams take turns at bat trying to score runs
round object that is hit or thrown or kicked in games
a spherical object used as a plaything
a solid projectile that is shot by a musket
a more or less rounded anatomical body or mass
one of the two male reproductive glands that produce spermatozoa and secrete androgens
a lavish dance requiring formal attire
a compact mass
an object with a spherical shape

ball (verb)	crystal ball (verb)
form into a ball by winding or rolling
to live very well