Openable windows are any windows which can be rotated, swung, slid, lifted, or otherwise moved between a sealed position and an open position which allows outside air to enter the building interior. They do not include balcony doors or other kinds of doors. In general, picture windows do not open while other window types do; stained glass windows may or may not be openable.

The opening is created by movement of the window itself. Rotation, swinging, sliding, or lifting are possible movements, rather than a requirement that every openable window use one particular mechanism.

Automatic window openers provide powered or controlled operation, while an openable window can also be operated manually. Balcony doors remain excluded even though opening one can also admit outside air.