The basics of geometry, lines, angles, planes, rays, are a great beginning. Geometry, which means earth measure is used to measure anything on earth. No matter what size a rectangle is, whether it be a computer chip, an Olympic-sized swimming pool, or a city block, you can always find its area by multiplying length by width. Readers also learn about polygons, triangles, circles, congruent figures, symmetry, and cones, as well as areas, perimeters, circumferences, volumes, and more.