As the name implies, troffers are trough-shaped recessed ceiling fixtures (the term is derived from the terms "trough" and "coffer." They usually contain fluorescent lamps and have an open surface flush with the ceiling. A parabolic troffer refers to a recessed fixture that has a louver with a parabolic cross section. The parabolic shape redirects light rays from the light source into parallel rays that shine in a controlled fashion into the room.

A long, recessed luminaire usually installed with the opening flush with the ceiling.

Recessed fluorescent fixture for use in a suspended ceiling; derived from the words "trough" and "coffer."