What is the difference between corsets and stays?

In books or websites, normally it would say either a stay or a corset. Someone can correct me if i'm wrong but I believe corsets and stays are the same things.

Here is the definition of a stay.

a device used as a brace or support.

• ( stays) historical a corset made of two pieces laced together and stiffened by strips of whalebone.

Here is a definition of a corset.

a woman's tightly fitting undergarment extending from below the chest to the hips, worn to shape the figure.

There might be a slight difference but that is my answer.