fracture vs break off

fracture is a noun but break off is not a noun.

Word	Noun	Adjective	Verb	Adverb
fracture	Yes	No	Yes	No
break off	No	No	Yes	No

As verbs, break off is a hypernym of fracture; that is, break off is a word with a broader meaning than fracture:

Other hypernyms of fracture include break, discontinue, stop.

fracture (noun)	break off (noun)
the act of cracking something
(geology) a crack in the earth's crust resulting from the displacement of one side with respect to the other
breaking of hard tissue such as bone

fracture (verb)	break off (verb)
fracture a bone of	prevent completion
become fractured	interrupt before its natural or planned end
violate or abuse	break a small piece off from
break into pieces	break off (a piece from a whole)
interrupt, break, or destroy	break a piece from a whole