clast vs fragment

clast and fragment both are nouns.

Word	Noun	Adjective	Verb	Adverb
clast	Yes	No	No	No
fragment	Yes	No	Yes	No

As nouns, fragment is a hypernym of clast; that is, fragment is a word with a broader meaning than clast:

clast (noun)	fragment (noun)
(geology) a constituent fragment of a clastic rock	a broken piece of a brittle artifact
	an incomplete piece
	a piece broken off or cut off of something else

clast (verb)	fragment (verb)
	break or cause to break into pieces