leg bone vs fibula

leg bone and fibula both are nouns.

Word	Noun	Adjective	Verb	Adverb
leg bone	Yes	No	No	No
fibula	Yes	No	No	No

As nouns, fibula is a hyponym of leg bone; that is, fibula is a word with a more specific, narrower meaning than leg bone:

leg bone: a bone of the leg
fibula: the outer and thinner of the two bones of the human leg between the knee and ankle

Other hyponyms of leg bone include femoris, femur, thighbone, calf bone, shin, shin bone, shinbone, tibia.

leg bone (noun)	fibula (noun)
a bone of the leg	the outer and thinner of the two bones of the human leg between the knee and ankle