Pertaining to the middle; in or toward the middle; nearer the middle of the body. Medial is as opposed to lateral. For example, the medial side of the knee is the side closest to the other knee whereas the lateral side of the knee is the outside of the knee. Within a multilayered structure, the center layer. The medial layer of the aorta is the middle layer. For example, necrosis of the medial layer of the aorta may lead to aortic rupture. See the entire definition of Medial
The side of the body or body part that is nearer to the middle or center (median) of the body. For example, when referring to the knee, medial would mean the side of the knee that is closest to the other knee The opposite of medial is lateral.