The word "惊愕" is formed by combining two characters, each constructed as a phono-semantic compound: "惊" uses the radical "忄" (heart-mind) to indicate an emotional state and the component "京" for its phonetic value, meaning "to frighten or surprise", while "愕" similarly uses "忄" with the phonetic "咢" to mean "astonished". Together, they create a disyllabic word where both characters contribute their meanings to express a state of shock or astoundment.