Which feature describes a somewhat spherical articular surface on the proximal end of long bones?

The feature that describes a somewhat spherical articular surface on the proximal end of long bones is known as a head. In anatomical terms, the head of a bone typically serves as the primary site for articulation with another bone, fitting snugly into a concave surface of a neighboring bone, allowing for smooth movement at the joint. The shape of the head, being spherical or rounded, facilitates a wide range of motion, essential for joint function.

In the context of the question, a trochanter refers to a large, blunt process found on the femur, primarily serving as muscle attachment sites rather than involving joint articulation. A condyle is a rounded prominence at the end of a bone that helps form a joint, but it is generally not described as spherical in the same way a head is. A facet, on the other hand, refers to a small, flat surface on a bone, which is not spherical and generally allows for limited movement between adjacent bones.

Thus, the head's unique spherical shape on the proximal end of long bones is what sets it apart, making it the correct description for this anatomical feature.