Difference between one way slab and two way slab in construction?

Ans: One way slab is the slab having ratio of longer span to shorter span equal to or more than 1.5 . If the ratio of longer span to shorter span is equal to or less than 1.5, then such slabs are called as two way slab.

In one way slab main tensile reinforcement is placed parellel to shorter side which will be the main steel, where as in two way slab both direction required main steel.