#index  a numerical scale used to compare variables with one another or with some reference number
  supertype:  scale_of_measurement__scale__graduated_table__graduatedtable__ordered_series  an ordered reference standard: "judging on a scale of 1 to 10"
  subtype:  margin_of_safety__safety_margin__margin_of_error  an index indicating the amount beyond the minimum necessary; "in engineering the margin of safety is the strength of the material minus the anticipated stress"

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