Also commonly referred to as a "suspended ceiling", a dropped ceiling is a system where the finished ceiling is lower than the actual ceiling. This system is most commonly manifested in the popular ACT (acoustic ceiling tiles) held in place in a tee-grid system. Commonly, panels of ACT will be removed, and registers, returns, lights, speakers, and various other tiles may be inset.

The dropping of a ceiling creates a plenum space, which allows for the easy installation, maintenance, and concealment of the HVAC and other building systems.