mezzanine

A secondary floor, in between the main floors of a building; entresol.

“On our way to the top floor, we stopped at the mezzanine.”

A small window used to light such a secondary floor.

The lowest balcony in an auditorium.

Additional flooring laid over a floor to bring it up to some height or level.

A floor under the stage, from which contrivances such as traps are worked.

Fulfilling an intermediate or secondary function.

“To make interconnections easier, we added a mezzanine PCB.”