Adjacent angles are two angles that share a vertex and a side but no points in their interiors.
alternate interior angles
Alternate interior angles are angles between two lines and on opposite sides of a transversal.
An angle bisector is a ray that divides a given angle into two congruent angles, each half the size of the given angle.
Complementary angles are two angles whose measures add to 90°.
Congruent angles are angles that have the same measure.
Congruent figures are figures that have the same size and shape. Congruent polygons have congruent corresponding sides and congruent corresponding angles. The symbol means "is congruent to."
Corresponding angles are pairs of nonadjacent angles that lie on the same side of a transversal of two lines and in corresponding positions.
Parallel lines are lines that lie in the same plane and do not intersect. The symbol || means "is parallel to."
A perpendicular bisector is a line, segment, or ray that is perpendicular to a segment at its midpoint.
Perpendicular lines are lines that intersect to form right angles.
A polygon is a closed plane figure with at least three sides.
A reflection is a transformation that flips a figure over a line of reflection.
A regular polygon is a polygon with all its sides congruent and all its angles congruent.
A rotation is a transformation that turns a figure about a fixed point, called the center of rotation. The angle measure of the rotation is the angle of rotation.
A segment is part of a line. It has two endpoints.
A segment bisector is a line, segment, or ray that separates a segment into two congruent segments.
Supplementary angles are two angles whose measures add to 180°.
A figure has reflectional symmetry when one half of the figure is a mirror image of the other half. The line of reflection is also called the line of symmetry.
A translation is a transformation that moves points the same distance and in the same direction.
Vertical angles are angles formed by two intersecting lines, and are opposite each other. Vertical angles are congruent.