“A Stair is a series of steps with or without landings or platforms, which is installed between two or more floors of a building to bridge a large vertical distance”.
A part of a building having series of steps is called stair case.
A part of the building accomodating the stair is known as stair case.
The structural member that supports the treads and risers. It is the part of the stairs that will hold all the weight.