#stair__step  support consisting of a place to rest the foot while ascending or descending a stairway; "he paused on the bottom step"
  supertype:  #support.device  any device that bears the weight of another thing; "there was no place to attach supports for a shelf"
  subtype:  #corbel_step  (architecture) a step or step-like projection on the top of a gable wall
  part of:  #stairway
  part:  #riser  structural member consisting of the vertical part of a stair or step
  part:  #tread  structural member consisting of the horizontal part of a stair or step

No statement uses or specializes #stair; click here to add one.