An opening in the wall of a building for the admission of light and air, usually closed by casements or sashes containing some transparent material, as glass, and capable of being opened and shut at pleasure.
- An opening constructed in a wall or roof that functions to admit light or air to an enclosure and is often framed and spanned with glass mounted to permit opening and closing.
- A framework enclosing a pane of glass for such an opening; a sash.
- A pane of glass or similar material enclosed in such a framework.
- An opening that resembles a window in function or appearance.
- The transparent panel on a window envelope.
- The area or space immediately behind a window, especially at the front of a shop.
- A means of access or observation: St. Petersburg was Peter the Great's window onto the Baltic.
- An interval of time during which an activity can or must take place: a brief window of opportunity for a space mission; a window of vulnerability during which the air force was subject to attack.
- Strips of foil dropped from an aircraft to confuse enemy radar; chaff.
- A range of electromagnetic frequencies that pass unobstructed through a planetary atmosphere.
- Computer Science A rectangular area on the screen that displays its own file or message independently of the other areas of the screen.
- Aerospace A launch window.
- Aerospace An area at the outer limits of the earth's atmosphere through which a spacecraft must pass in order to return safely.