CORRIDOR, a main passage in a large building, on which various apartments open (Med. Lat. corridorium, a "running place," from currere, to run) . In public offices, prisons, hospitals, etc., the corridors are usually of severe simplicity; but in mansions and palaces large corridors (galleries) are often adorned with works of art, whence comes the term "picture gallery." The term "corridor carriage" is applied to the modern European style of railway carriage in which a narrow passage connects the sepa rate compartments.