| A | B |
|---|
| Acute angle | Angle with measure less than 90 degrees |
| Adjacent angles | Angles with a common vertex, common side and no interior points in common |
| Angle | Union of two rays with common end point that are non-collinear |
| Bisect | To cut in two equal parts |
| Complementary angles | Two angles with a sum of 90 degrees |
| Congruent | Two figures with equal measure |
| Line | A series of points that extend in opposite directions without end |
| Midpoint | Point that divides a segment into two equal parts |
| Obtuse angle | Angle with measure greater than 90 degrees |
| Parallel lines | Lines in the same plane that don't intersect |
| Perpendicular lines | Two lines that intersect to form right angles |
| Plane | A flat surface with no thickness that extends indefinitely in all directions |
| Point | A position in space with no size |
| Ray | A part of a line that is bounded by one endpoint |
| Right angle | Angle with measure of 90 degrees |
| Segment | A part of a line that is bounded by two endpoints |
| Skew lines | Non-coplanar lines that do not intersect |
| Supplementary angles | Two angles with a sum of 180 degrees |
| Vertex | The common endpoint of two rays or segments |
| Vertical angles | Two non-adjacent angles formed when two lines intersect |
| Acute triangle | Triangle with all acute angles |
| Altitude | Any line segment from a vertex perpendicular to the base, also the height of a figure |
| Equilateral triangle | Triangle with all sides equal |
| Isosceles triangle | Triangle with at least two equal sides |
| Median (triangle) | In a triangle, the segment that joins a vertex and the midpoint of the opposite side |
| Obtuse triangle | Triangle with one obtuse angle |
| Right triangle | Triangle with a right angle |
| Scalene triangle | Triangle with no equal sides |
| Similar | Figures with corresponding angles congruent and corresponding sides in equal rations |
| Diagonal | A segment that connects nonconsecuive vertices of a polygon |
| Hexagon | Six sided figure |
| Parallelogram | Polygon with opposite sides that are parallel |
| Pentagon | Polygon with five sides |
| Polygon | Plane figure with segments for sides |
| Quadrilateral | Four sided polygon |
| Regular polygon | A polygon with all sides and angles congruent |
| Rhombus | Quadrilateral with four equal sides |
| Trapezoid | Quadrilateral with one pair of parallel sides |
