in physics, any location within a solid (generally a semiconductor or an insulator) that restricts the movement of electrons (electron) and holes (hole)—i.e., equivalent positive electrical charges that result from the absence of an electron within a crystal structure. A trap consists of either a chemical impurity or an imperfection in the regular spacing of the atoms that make up the solid. Traps play a significant role in photoconduction, luminescence, and the operation of various electronic devices because the ability of a solid to carry an electrical current depends on the flow of electrons and holes through the solid.

A trap can capture and immobilize an electron or hole and prevent its recombination with the carrier of opposite charge as an electron-hole pair. Electrons and holes may break free from traps quickly, or they may remain there for an extended period of time (e.g., several months or longer). Charge carriers can be released from traps by the addition of energy, such as irradiating the solid with light or by heating it.

in theatre, a concealed opening, usually in the stage floor, through which actors, props, and scenery can be brought on and off stage. Traps are used, often with elaborate and ingenious machinery, to create a great variety of stage effects, particularly the sudden appearance, disappearance, or apparent transformation of characters or objects on the stage.

Certain types of traps have become more or less standard items of stage equipment. The corner trap, for example, is a small, square opening, usually located at the side of the stage, fitted with a trapdoor or flaps that can be lowered out of sight. Through it, standing figures or objects can be lifted onto the stage. When a sudden, mysterious appearance is required, a star trap is used. The star trap is a circular opening with a lid composed of wedge-shaped sections, individually hinged to the circumference. An actor, standing below on a heavily counterweighted platform, can be projected through the opening with great speed. The sections of the lid are pushed up as he passes and immediately fall back into place, thus concealing his point of entrance. Another common trap with a long history is the grave trap, a large, rectangular opening in the centre of the stage floor. It is named for its most famous use, as an open grave in the graveyard scene from Hamlet. Most traps and their mechanisms are designed so that they can be taken apart and moved to any point in the stage floor where they are required or can be stored when not in use.