-cephalic Also -cephalous, -cephalus, and -cephaly.
[Greek kephalē, head.]
Adjectives in -cephalic and -cephalous are usually equivalent in meaning, though the former is more common. Examples are hydrocephalic (literally, having water on the head) in reference to a child suffering from an enlarged head because of fluid retention; brachycephalic (Greek brakhus, short), having a relatively broad, short skull; microcephalic (Greek mikros, small), abnormal smallness of the head, a congenital condition associated with incomplete brain development; bicephalous (Latin bi, having two), having two heads.
Nouns in -cephalus or -cephaly refer to the condition: hydrocephalus; microcephaly; macrocephalus; plagiocephaly (Greek plagios, slanting), oblique deformity of the head. With the exception of hydrocephalus, forms in -cephalus are generally less common than those in -cephaly.