Which prefix refers to the head?

The prefix that refers to the head is "cephal." This prefix originates from the Greek word "kephalē," meaning head. It is commonly used in various medical and scientific terminologies to indicate a relation to the head. For example, terms like "cephalalgia" refer to a headache, highlighting its connection to the head.

The other options represent different anatomical or descriptive concepts. "Poly" is a prefix meaning many or multiple, often used in terms like "polygamous" or "polyatomic." "Cardi" refers to the heart, derived from the Greek "kardia," and is found in words such as "cardiology." "Supra" indicates above or over, as in "suprarenal" (above the kidneys). Therefore, "cephal" is the specific prefix associated with the head, making it the correct choice.