Cephal

Cephal is a combining form derived from the Greek kephalē, meaning head. In English medical and scientific terminology, cephal- or cephalo- introduces terms related to the head and its structures. It functions as a prefix or bound morpheme in compound words and is not typically used as an independent word.

Common terms created with cephal- include cephalad (toward the head), cephalic (relating to the head), cephalometry (measurement of the head), cephalogram (an X-ray image of the head), and cephalalgia (headache). In obstetrics, cephalic presentation refers to a fetus positioned head-first for delivery. Other related phrases describe parts of the head, such as cephalic vein or cephalic index.

In zoology and anatomy, cephal- denotes the head region; cephalon refers to a head segment in certain arthropods and fossils, such as trilobites, while cephalothorax denotes the fused head and thorax found in spiders and many crustaceans. The distinction between cephal- and cranio- is subtle: cranio- often emphasizes the skull, whereas cephal- more broadly denotes the head.

Related concepts include cephalization—the concentration of nervous and sensory tissues at the anterior end to form a head—and the continued use of the prefix across biology, medicine, anatomy, and anthropology. The term reflects historical naming conventions that link structure to the head as a central feature of organisms.