if LY/LX>2 than we use one way slab if <2 than use two way slab.One way slab supported only two direction and two way slab supported in all four direction.

1. one way slab

2. two way slab

3. flat slab

4. roof slab

The different types of slabs are; one way slab, two way slab, flat plated slab, flat slab and grid slab

the ratio of Length of span / width of span = >2 or <2

Or where span of Slab is with in 3.6 m it is one way slab,

and where span is more than 3.6 m it is two way slan.

when l/b ratio more than or equal to 2 then slab is designed as one way and when l/b ratio is less than 2 then slab is designed as two way.