The word "癫痫" is formed by combining two characters, each constructed with the "疒" radical denoting illness. The character "癫" incorporates "颠" for both phonetic approximation and semantic association with mental disturbance, while "痫" uses "间" primarily as a phonetic element to guide pronunciation. Together, they create a compound term specifically referring to the neurological disorder epilepsy, with the shared radical emphasizing its medical nature.