femur vs thighbone

femur and thighbone both are nouns.

Word	Noun	Adjective	Verb	Adverb
femur	Yes	No	No	No
thighbone	Yes	No	No	No

As nouns, femur and thighbone are synonyms defined as:

femur and thighbone: the longest and thickest bone of the human skeleton; extends from the pelvis to the knee

Other synonyms of femur include femoris.

femur (noun)	thighbone (noun)
the longest and thickest bone of the human skeleton; extends from the pelvis to the knee	the longest and thickest bone of the human skeleton; extends from the pelvis to the knee