angle

The distance between two rays sharing a common endpoint or two lines that intersect. An angle has one vertex and two sides.

angles of a circle

The angles formed within a circle. All angles in a circle add up to 360 degrees.

area

The size of the space contained within an enclosed twodimensional figure. Area is typically measured in square units such as square inches or square centimeters.

bolt hole pattern

A pattern used on some workpieces in which a series of holes are formed around an imaginary center.

central angle

An angle formed within a circle in which the center of the circle is the vertex and the sides of the angle are radii.

circle

The figure formed by the group of points that are an equal distance from a point, or center. The angles of a circle add up to 360 degrees.

circumference

The boundary or perimeter around a circle. Circumference measures the distance around a circle.

concave polygon

A polygon in which at least one of the angles is greater than 180 degrees.

convex polygon

A polygon in which all angles are less than 180 degrees.

diameter

The distance from one edge of the circle to the opposite end through the center. The radius is half the diameter.

hexagon

A polygon with six sides.

perpendicular

Two lines that intersect to form a 90° angle.

pi

A special constant value that relates the diameter of a circle to its circumference. Pi, roughly 3.14, is used to find the circumference and area of a circle.

point of tangency

The point at which the tangent touches the circle.

polygon

A closed shape consisting of line segments that has at least three sides. Triangles, quadrilaterals, rectangles, and squares are all types of polygons.

quadrilateral

A polygon with four sides.

radii

The plural for radius. All radii on a given circle are equal in length.

radius

The distance from the center to the edge of a circle. If you multiply the radius of a circle by two, the result is the diameter.

ratio

The relationship between two quantities expressed as a fraction.

regular polygon

A polygon in which all angles and sides are equal.

semicircle

A halfcircle. The angles of a semicircle add up to 180 degrees.

square

The product of multiplying a number by itself.

tangent

A line, line segment, or ray that touches a circle at exactly one point.

tangent point

Another way to describe the point of tangency.

triangle

A polygon with three sides.

vertex

The point of an angle where its two sides meet.

vertical angle

Two angles that share the same vertex and are positioned directly opposite one another. Vertical angles are formed whenever two lines intersect.

vertical angles

Two angles that share the same vertex and are positioned directly opposite one another. Vertical angles are formed whenever two lines intersect.
