What Stairs are

Flight: It is a series of steps without a platform or landing or a break in their direction.
Tread: It is the upper horizontal part of a step on which the foot is placed when ascending or descending stairs.
Step: This is the part of the staircase that involves walking and rising. It allows to ascend or descend from one floor to another.
Riser: It is a vertical member between two legs. It provides support for walking.

Rise: It is the vertical distance between the upper faces of any two consecutive steps.
Flyer: This is a straight step that runs parallel to the width.
Landing: It is a platform provided between two flights.
Nosing: It is the outer projection edge of a tread. It is usually rounded to give an appearance that is more pleasing and makes the stairs easier to negotiate.
Walk: It is the width of walk between two consecutive risers. In other words it is the horizontal distance between the faces of two consecutive risers.
Winder: These are tapering steps used to change the direction of stairs.
String or Stringer: It is a sloped member that supports the rungs in a ladder

Soffit: This is the underside of a stair.

Header: This is a horizontal structural member supporting stair stringers or landings.

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