(in Russian, sektsionnye doma), a multiapartment dwelling composed of several mutually adjoining modules—groups of rooms identical on each floor and arranged around common stairwells or elevators. The modules can be classified according to their location on the building plan into row, butt, or corner modules, or they may be classified according to their orientation as latitudinal or meridional modules. The combination of various kinds of modules for apartments with various numbers of rooms is determined by demographic statistics. Such combinations provide solutions to many architectural problems. Modular apartment buildings are the most common type of urban dwelling in the USSR.