| A | B |
|---|
| Undefined term | A basic figure that is not defined in terms of other figures. |
| Collinear | Points that lie on the same line. |
| Plane | A flat surface that has no thickness and extends forever. |
| Line | A straight path that has no thickness and extends forever. |
| Point | A location that has no size. |
| Coplanar | Points that lie in the same plane. |
| Endpoint | A point at an end of a segment or the starting point of a ray. |
| Ray | A part of a line that starts at an endpoint and extends forever in one direction. |
| Postulate | A statement that is accepted as true without proof, also called an axiom. |
| Vertex | The common endpoint of the sides of an angle. |
| Opposite rays | Two rays that have a common endpoint and form a line. |
| Segment | A part of a line consisting of two endpoints and all points between them. |
| Distance | The absolute value of the difference of the coordinates of two points. |
| Construction | A method of creating a figure that is considered to be mathematically precise. |
| Between | Given three points A, B, and C, B is between A and C if and only if all three of the points lie on the same line, and AB + BC = AC. |
| Coordinate plane | A plane that is divided into four regions by a horizontal line called the x-axis and a vertical line called the y-axis. |
| Coordinate | A number used to identify the location of a point. |
| Congruent segments | Two segments that have the same length. |
| Degree | A unit of angle measure. |
| Midpoint | The point that divides a segment into two congruent segments. |
| Bisect | To divide into two congruent parts. |
| Angle | A figure formed by two rays with a common endpoint. |
| Measure | The use of units to find a size or quantity. |
| Segment bisector | A line, ray, or segment that divides a segment into two congruent segments. |
| Vertical angles | The nonadjacent angles formed by two intersecting lines. |
| Straight angle | An angle formed by two opposite rays that measures 180°. |
| Acute angle | An angle that measures greater than 0° and less than 90°. |
| Right angle | An angle that measures 90°. |
| Interior of an angle | The set of all points between the sides of an angle. |
| Obtuse angle | An angle that measures greater than 90° and less than 180°. |
| Exterior of an angle | The set of all points outside an angle. |
| Adjacent angles | Two angles in the same plane with a common vertex and a common side, but no common interior points. |
| Complementary angles | Two angles whose measures have a sum of 90°. |
| Supplementary angles | Two angles whose measures have a sum of 180°. |
| Angle bisector | A ray that divides an angle into two congruent angles. |
| Linear pair | A pair of adjacent angles whose noncommon sides are opposite rays. |
| Congruent angles | Angles that have the same measure. |
| Image | A shape that results from a transformation of a figure. |
| Preimage | The original figure in a transformation. |
| Reflection | A transformation across a line. |
| Transformation | A change in the position, size, or shape of a figure. |
| Rotation | A transformation about a point P, such that each point and its image are the same distance from P. |
| Translation | A transformation in which all the points of a figure move the same distance in the same direction. |
| leg | One of the two sides of the right triangle that form the right angle. |
| Area | The number of nonoverlapping unit squares of a given size that will exactly cover the interior of a plane figure. |
| Hypotenuse | The side opposite the right angle in a right triangle. |
| Length | The distance between the two endpoints of a segment. |
| base | Any side of a triangle. |
| Height | Asegment from a vertex that forms a right angle with a line containing the base. |
| Radius | A segment whose endpoints are the center of a circle and a point on the circle, or the distance from the center of a circle to any point on the circle. |
| Perimeter | The sum of the side lengths of a closed plane figure. |
| pi | The ratio of the circumference of a circle to its diameter, denoted by the Greek letter π. |
| Circumference | The distance around the circle. |
| Diameter | A segment that passes through the center of a circle and whose endpoints are on the circle, or the length of such a segment. |
