Slab
Slabs are constructed to provide flat surfaces, usually horizontal, in building floors, roofs, bridges, and other types of structures. Walls may support the slab by reinforced concrete beams usually cast monolithically with the slab, by structural steel beams, by columns, or by the ground.
One Way Slab
One way slab is a slab that is supported by beams on the two opposite sides to carry the load in one direction. The ratio of longer span (l) to shorter span (b) is equal or greater than 2, considered a One-way slab because this slab will bend in one direction, i.e., along its shorter span.
Due to the huge difference in lengths, the load is not transferred to the shorter beams. Main reinforcement is provided in a shorter span, and distribution reinforcement in a longer span.
Two Way Slab
Beams support a two-way slab on all four sides, and the supports carry the loads along with both directions. It is known as a two-way slab. In two way slab, the ratio of longer span (l) to shorter span (b) is less than 2.
In two-way slabs, the load will be carried in both directions. So, the main reinforcement is provided in both directions for two-way slabs.