hairline fracture vs capillary fracture

hairline fracture and capillary fracture both are nouns.

Word	Noun	Adjective	Verb	Adverb
hairline fracture	Yes	No	No	No
capillary fracture	Yes	No	No	No

As nouns, hairline fracture and capillary fracture are synonyms defined as:

hairline fracture and capillary fracture: a fracture without separation of the fragments and the line of the break being very thin

hairline fracture (noun)	capillary fracture (noun)
a fracture without separation of the fragments and the line of the break being very thin	a fracture without separation of the fragments and the line of the break being very thin