What anatomical term would best describe a structure on the side of the body?

The term that best describes a structure on the side of the body is "lateral." In anatomical terminology, lateral refers to a position that is farther from the midline of the body, indicating that the structure is located more towards the outer side rather than the center. For example, your arms are lateral to your torso, as they are positioned on either side of the body.

In contrast, medial is used to describe a position closer to the midline, which would not fit the definition of being on the side. Inferior refers to a position lower on the body, typically used in reference to vertical positioning, and proximal denotes a position closer to a point of attachment or origin, usually in relation to limbs. Thus, "lateral" is the most accurate term for describing structures on the side of the body.