What is the only medical term that describes lying down?

The term "recumbent" specifically refers to a position of lying down or reclining. In medical terminology, being recumbent indicates that an individual is resting or positioned horizontally, which can be important in various clinical assessments and treatments. This term is widely used in healthcare settings to describe the physical state of patients, especially when assessing their comfort or the need for assistance.

In contrast, the other terms refer to different concepts: "adduction" involves moving a body part closer to the midline of the body, "flexion" refers to decreasing the angle between two body parts, and "abduction" means moving a body part away from the midline. These actions relate more to movement and positioning rather than the overall state of lying down. Therefore, the correct choice highlighting the action of being in a recumbent position is appropriate and accurately reflects the described medical term.