FTCE General Knowledge Math Practice Test 2025 – 400 Free Practice Questions to Pass the Exam

The term for a closed two-dimensional shape with straight sides is a polygon. Polygons are defined by having multiple sides and vertices, and they can take various forms such as triangles, quadrilaterals, pentagons, and so on. Each side of a polygon is a straight line segment, and the figure itself is enclosed, distinguishing it from other shapes like circles or ellipses, which have curved sides.

The other terms listed do not describe closed shapes with straight sides: "diameter" refers to a line segment that passes through the center of a circle, connecting two points on the circle; "circle" is a shape where all points are equidistant from a central point and does not have straight sides; "ellipse" is a closed curve but also made up of curved lines rather than straight segments. Hence, the correct terminology for closed two-dimensional shapes with straight sides is indeed polygon.