English Convex and concave polygons convex convex polygon convex چند ضلعی مقعر re-entrant angles چند ضلعی مقعر Wikipedia convex polygon (see Wikipedia) Wiki’s definition https://en.wikipedia.org/wiki/Convex_and_concave_polygons concave polygon concave polygons convex polygon (see Wikipedia) Convex and concave polygons convex polygon