# Kids Math

## Glossary and Terms: Figures and Shapes

For more detailed information and diagrams on specific shapes see the Polygons, Quadrilaterals, Triangles, Pythagorean Theorem, Circle, Perimeter, and Surface Area pages.

Arc - A portion of the circumference of a circle.

Base - The bottom line of a shape.

Center - In a circle, the center is the point that is the same distance from all points on the circumference.

Chord - Any line that connects two points on the circumference of a circle.

Circle - A simple shape made up of all the points on a plane that are the same distance from a single point.

Circumference - The perimeter of a circle or the distance around the outside of a circle.

Closed figure - Any figure that has the same start and end point is a closed figure.

Concentric - Objects with the same center are considered concentric.

Cone - A three dimensional object that has a flat circular base that tapers to a single point.

Congruent - Figures are said to be congruent if they have the same shape and size.

Cube - A cube is a three dimensional object bound by six identical squares.

Cylinder - A cylinder is a three dimensional object with two parallel bases (which are usually circles) connected by a curved surface.

Diameter - A line segment that passes through the center of a circle with each end point being on the circumference.

Ellipse - An ellipse is a closed curve where the distance from two fixed points to any point on the curve add to the same constant. The circle is a special type of ellipse.

Equiangular - When all angles inside a polygon are the same, it is said to be equiangular. A square and an equilateral triangle are equiangular.

Face - One side or plane of a three dimensional object.

Hypotenuse - The longest side of a right triangle. It is the side opposite from the right angle.

Irregular polygon - A polygon with sides of all different lengths and angles of all different degrees.

Open figure - A two-dimensional object that is not closed.

Parallelogram - A quadrilateral with two sets of parallel sides. Opposite sides are the same length and opposite angles are equal in a parallelogram.

Perimeter - The distance around the outside of a two dimensional figure.

Pi - A special constant number used for figuring the circumference and diameter of a circle. It goes on forever but can be shortened to 3.14159.

Polygon - A closed figure made up of straight lines. Polygons with different numbers of sides have their own names. See the polygon page for more on polygons.

Polyhedron - A three-dimensional object composed of flat faces and straight lines.

Prism - A three-dimensional object with ends that are parallel and congruent as well as sides that are parallelograms.

Pythagorean theorem - A formula used to calculate the length of the sides in a right triangle. It is a2 + b2 = c2 where a and b are two sides of the right triangle and c is the hypotenuse.

Radius - A line segment from the center of a circle to the outside border.

Rectangle - A quadrilateral, or four sided polygon, with four right angles.

Regular polygon - A polygon where all of the sides have the same length and all of the angles are equal in measure.

Rhomboid - A rhomboid is a parallelogram where the adjacent sides are not equal.

Rhombus - A rhombus is a parallelogram where all four sides are the same length.

Similar figures - Similar figures have the same shape, but different sizes.

Sphere - A three-dimensional object where every point is the same distance from the center. A basketball is a sphere.

Square - A rectangle where all four sides are the same length.

Surface area - The total sum of all the surfaces of a three-dimensional object.

Trapezoid - A quadrilateral with only one pair of parallel sides.

Vertex - A point of intersection for lines or segments.

More Math Glossaries and Terms

Algebra glossary
Angles glossary
Figures and Shapes glossary
Fractions glossary
Graphs and lines glossary
Measurements glossary
Mathematical operations glossary
Probability and statistics glossary
Types of numbers glossary
Units of measurements glossary

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