The word 弹壳 is formed by combining two characters, each contributing a clear visual and functional concept. 弹 (dàn) means "bullet" or "projectile", while 壳 (ké) means "shell" or "casing". When placed together, they create a direct, compound image where the meaning of the second character (壳) physically contains and defines the first (弹), resulting in the concrete object: the "bullet casing" or "cartridge case", the hollow shell that remains after the bullet is fired.