#stairway__staircase__stairs__steps__step  a way of access consisting of a set of steps
  supertype:  way  any artifact consisting of a road or path affording passage from one place to another; "he said he was looking for the way out"
  subtype:  backstairs  companionway  escalator  fire_escape  flight_of_stairs  ghat  ladder
  part of:  edifice
  part:  landing.platform  an intermediate platform in a staircase
  part:  stairhead  platform at the top of a staircase
  part:  stair__step  support consisting of a place to rest the foot while ascending or descending a stairway; "he paused on the bottom step"
     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

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