The word "寝室" is formed by combining the character "寝", meaning to sleep or rest, which itself incorporates the radical "宀" for roof and elements associated with lying down, with the character "室", meaning room or chamber, composed of "宀" for roof and "至" indicating arrival or enclosure. Together, they directly denote a room designated for sleeping, with "寝" defining the purpose and "室" specifying the enclosed space.