Stairs

Stairs are a structure designed to bridge a large vertical distance between lower and higher levels by dividing it into smaller vertical distances. This is achieved as a diagonal series of horizontal platforms called steps which enable passage to the other level by stepping from one to another step in turn. Steps are very typically rectangular. Stairs may be straight, curved, or may consist of two or more straight pieces connected at angles.

Types of stairs include staircases (also called stairways) and escalators. Some alternatives to stairs are elevators (also called lifts), stairlifts, inclined moving walkways, ladders, and ramps. A stairwell is a vertical shaft or opening that contains a staircase. A flight (of stairs) is an inclined part of a staircase consisting of steps (and their lateral supports if supports are separate from steps).

This is an excerpt from Staircase.

The concept of stairs is believed to be 8000 years old, and is one of the oldest structures in architectural history. The oldest example of spiral stairs dates back to the 400s BC. Medieval architecture saw experimentation with many different shapes, and the Renaissance even more so with varied designs.

A stair, or a stairstep, is one step in a flight of stairs. A staircase or stairway is one or more flights of stairs leading from one floor to another, and includes landings, newel posts, handrails, balustrades, and additional parts.

In buildings, stairs is a term applied to a complete flight of steps between two floors. A stair flight is a run of stairs or steps between landings. A stairwell is a compartment extending vertically through a building in which stairs are placed. A stair hall is the stairs, landings, hallways, or other portions of the public hall through which it is necessary to pass when going from the entrance floor to the other floors of a building. Box stairs are stairs built between walls, usually with no support except the wall strings.

Stairs may be in a "straight run", leading from one floor to another without a turn or change in direction. Stairs may change direction, commonly by two straight flights connected at a 90° angle landing. Stairs may also return onto themselves with 180° angle landings at each end of straight flights forming a vertical stairway commonly used in multistory and highrise buildings. Many variations of geometrical stairs may be formed of circular, elliptical and irregular constructions.

Ascending a set of stairs to a higher floor is often referred to as going "upstairs", the opposite being "downstairs". The same words can also be used to mean the upper or lower floors of a building, respectively.