Which term describes movement "toward the midline of the body"?

The term that describes movement "toward the midline of the body" is medial. In anatomical terminology, "medial" refers to a position or movement that is closer to the center of the body or the midline. For example, if one were to raise their arms and then bring them closer together toward the center of their body, this would be a medial movement.

Understanding the concept of medial is essential in biomechanics, as it helps to describe and analyze movements and positions accurately. The other terms offered differ significantly in their meanings: proximal refers to being closer to the trunk or the point of origin of a limb; rectilinear pertains to movement in a straight line; and posterior describes a position toward the back of the body. Thus, recognizing that medial specifically refers to movement toward the midline clarifies its use in describing physical movements and anatomical locations.