For purposes of this chapter the following words and phrases shall have the following meanings ascribed to them respectively.
(a) "Apartment building" means a multi-family dwelling comprised of three or more dwelling units arranged side by side and/or one above the other, and each unit having a separate entrance or entrances connected to a common outside entrance or entrances.
(b) "Main wall" means any interior wall containing the principal windows of a living, dining or sleeping room or rooms, and/or other windows.
(c) "Secondary wall" means an exterior wall, other than a main wall, containing minor windows of a dining or sleeping room, or principal or minor windows of a kitchen or bathroom, or a blank surface.
(d) "Wall unit" means each vertical plane of a building shall be considered a separate wall in applying those yard regulations.
(e) "Overlapping walls" means those portions of the exterior wall or walls which are directly opposite when two buildings, parallel, or within thirty degrees of parallel, face each other across an open yard or space.
(f) "Single development" means one multi-family building located on a zoning lot which abuts a public street.
(g) "Group development" means one multi-family building located on a zoning lot which may or may not be developed in the usual street and lot pattern.
(1973 Code Section 151.10.)