| A | B |
|---|
| Point | Usually represented by a small dot & identified by a letter; it has no dimension |
| Line | An endless straight path; represented by a straight line with two arrowheads |
| Line Segment | Part of a line between two endpoints |
| Ray | A part of a line that has one endpoint (initial point) and goes forever in one direction |
| Plane | An endless flat surface; usually represented by a shape like a tabletop or wall |
| Vertex | The point where two rays meet, creating an angle |
| Acute Angle | An angle that measures less than ninety degrees |
| Right Angle | An angle that measures exactly ninety degrees |
| Obtuse Angle | An angle that measures greater than 90 degrees but less than 180 degrees |
| Conjecture | An unproven statement based on observations |
| Inductive Reasoning | The process of looking for patterns and making conjectures |
| Counterexample | An example that shows that a conjecture is false |
| Collinear Points | Points that lie on the same line |
| Coplanar Points | Points that lie on the same plane |
| Opposite Rays | Two rays with a common initial point (endpoint) that extend in opposite directions |
| Intersection | The set of points the figures have in common |
| Protractor | The semicircular instrument used to measure and/or construct an angle |
| Postulates (Axioms) | Rules that are accepted without proof |
| Coordinate | The real number that corresponds to the point |
| Distance (Length) | The absolute value the difference between the coordinates of two points |
| Between | When three points lie on a line, you can say that one of them is between the other two |
| Distance Formula | The formula for computing the distance between two points in a coordinate plane |
| Congruent Segments | Segments that have the same length |
| Angle | Two different rays that have the same initial point |
| Sides of an Angle | The rays that make up an angle |
| Congruent Angles | Angles that have the same measure |
| Interior of an Angle | Points that lie between the two sides of an angle |
| Exterior of an Angle | Points that lie outside the two sides of an angle |
| Adjacent Angles | Two angles that share a common vertex and side, but have no common interior points |
| Midpoint | The point that divides a segment into two congruent segments |
| Segment Bisector | A segment, ray, line, or plane that intersects a segment at its midpoint |
| Angle Bisector | A ray that divides an angle into two adjacent angles that are congruent |
| Straightedge | A ruler without marks |
| Construction | A drawing that uses a straightedge and compass |
| Compass | A tool used to create circles and arcs |
| Vertical Angles | Two angles whose sides for two pair of opposite rays |
| Linear Pair | Two adjacent angles whose noncommon sides are opposite rays |
| Supplementary Angles | Two angles whose sum is 180 degrees |
| Complementary Angles | Two angles whose sum is 90 degrees |
| Supplement | The 2nd of two numbers that add up to be 180 |
| Complement | The 2nd of two numbers that add up to be 90 |
