fenestration

Short definition from Wiktionary

Noun

1. 1
   The arrangement of windows and similar openings in a building.
2. 2
   An opening in the surface of an organ etc; the surgical creation of such an opening, especially one in the bony part of the inner ear made to improve hearing.
3. 3
   An opening that occurs naturally or is created surgically, as through a biological membrane.
4. 4
   Either a translucent area in a structure such as a leaf or flower petal, or an opening in a structure.
5. 5
   The practice of placing holes in the rudder of a ship to reduce the work required to move the rudder while preserving its ability to steer the ship.