device

(noun) an instrumentality invented for a particular purpose. Examples: "The device is small enough to wear on your wrist." "A device intended to conserve water."

(noun) something in an artistic work designed to achieve a particular effect.

(noun) any clever maneuver. Synonyms: gimmick, twist. Examples: "He would stoop to any device to win a point." "It was a great sales gimmick." "A cheap promotions gimmick for greedy businessmen."

(noun) any ornamental pattern or design (as in embroidery).

(noun) an emblematic design (especially in heraldry). Example: "He was recognized by the device on his shield."