Medical Definition of femur
plural fe·murs or fem·o·ra \ˈfem-(ə-)rə\play
1: the proximal bone of the hind or lower limb that is the longest and largest bone in the human body, extends from the hip to the knee, articulates above with the acetabulum by a rounded head connected with the shaft of the bone by an oblique neck bearing a pair of trochanters for the attachment of muscles, and articulates with the tibia below by a pair of condyles—called also thigh bone
2: the segment of an insect's leg that is third from the body
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