S: (n) plane (plane%1:25:00::), sheet (sheet%1:25:00::) ((mathematics) an unbounded two-dimensional shape) "we will refer to the plane of the graph as the X-Y plane"; "any line joining two points on a plane lies wholly on that plane"
S: (n) triangle (triangle%1:25:01::) (something approximating the shape of a triangle) "the coastline of Chile and Argentina and Brazil forms two legs of a triangle"