What thickness characteristic defines a two-way flat plate slab?

A two-way flat plate slab is characterized by its uniform thickness in two or more directions, which allows for the distribution of loads across the slab. This design provides structural integrity and minimizes deflection, making it suitable for various architectural applications.

The uniform thickness contributes to its ability to span in both directions without requiring additional support, making it efficient for both gravity and lateral loads. This characteristic is particularly advantageous in the design of large spaces where columns or beams are not preferable due to aesthetic considerations or space functionality.

The other options do not accurately define a two-way flat plate slab. Varying thickness would typically imply a design that might compromise structural efficiency, whereas ornamental edges or thickened corners do not reflect the core characteristic of having a two-dimensional uniform thickness that is essential for the performance and application of this slab type.