Stair Pitch

The Pitch is the angle between the pitch line and the horizontal where the Pitch Line is the line connecting the nosings of all treads in a flight of stairs. The slope or pitch of the stairs is the total rise divided by the total run or going (not the individual riser or treads due to the nosing) and is sometimes called the rake of the stairs. The pitch line is the imaginary line along the tip of the nosing of the treads. Consistency in the pitch, going and rise of stairs is an important safety factor as it reducles the trip hazard.

WIKIPEDIA ENTRY FOR STAIRWAY.

Stair Pitch Picture