WHAT IS ONE WAY SLAB
A slab is supported only one direction that is one way slab now tha loads are transferred only this two supports .therefore the main reinforcements are provided perpendicular to supported direction.
Also the slab is supported four sides but the length breadth ( ly/lx)ration is greater than or equal to two , the slab is designed as one way slab. Therefore assumed the loads are transferred only one direction and designed that slab is one way slab.