#arch  (architecture) a masonry construction (usually curved) for spanning an opening and supporting the weight above it
  supertype:  physical_structure__structure__construction  a thing constructed; a complex construction or entity; "the structure consisted of a series of arches"; "she wore her hair in an amazing construction of whirls and ribbons"
  subtype:  abutment_arch  broken_arch  camber_arch  corbel_arch  flat_arch  pier_arch  pointed_arch  proscenium_arch  rampant_arch  round_arch  rowlock_arch  safety_arch  scoinson_arch  shouldered_arch  skeen_arch  skew_arch  squinch  trimmer_arch  triumphal_arch  Tudor_arch
  part of:  aqueduct  arcade.structure  bridge
  part:  keystone__headstone  the central building block at the top of an arch or vault
  part:  springer__impost  the lowest stone in an arch -- from which it springs
  part:  voussoir  wedge-shaped stone building block used in constructing an arch or vault

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