Which term refers to something that is situated in the middle?

The term that refers to something situated in the middle is "pertaining to the middle." This indicates a position that is centrally located, often used to describe concepts, structures, or measurements that are equidistant from the endpoints or boundaries. In various contexts, whether anatomical, geographical, or in general descriptors, knowing that "middle" signifies a central point helps in understanding spatial relationships or hierarchies.

The other choices pertain to different positions: "pertaining to the end" refers to objects or points located at the far side of a spectrum, "pertaining to the outer" emphasizes locations at the periphery, and "pertaining to the top" denotes an uppermost position. Therefore, selecting "pertaining to the middle" accurately captures the essence of being centrally located.