A tool with two arms joined at their ends which can be used to draw circles. In geometric constructions, the classical Greek rules stipulate that the compass cannot be used to mark off distances, so it must "collapse" whenever one of its arms is removed from the page. This results in significant complication in the complexity of geometric constructions.
Compass
See also
Constructible Polygon, Euclidean Tools, Geometric Construction, Geometrography, Mascheroni Construction, Plane Geometry, Polygon, Poncelet-Steiner Theorem, Ruler, Simplicity, Steiner Construction, StraightedgeExplore with Wolfram|Alpha
References
Dixon, R. "Compass Drawings." Ch. 1 in Mathographics. New York: Dover, pp. 1-78, 1991.Referenced on Wolfram|Alpha
CompassCite this as:
Weisstein, Eric W. "Compass." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/Compass.html