Acute Angle: An acute angle is an angle whose measure is between zero and 90 degrees.
Adjacent Angles: Two coplanar angles with a common side, vertex, and no interior points.
Angle: Formed by two rays with the same endpoint. The rays are the sides of the angle and the common endpoint is the vertex.
Angle Bisector: A ray that divides an angle into two congruent angles.
Collinear: Points that lie on the same line.
Compass: A geometric tool used to draw circles and arcs.
Complementary Angles: Two angles, the sum of whose measure is 90 degrees.
Congruent Angles: Angles with the same measure.
Congruent Segments: Two segments with the same length.
Conjecture: A conclusion reached by inductive reasoning.
Construction: Uses a straight edge and a compass to make geometric figures.
Coordinate: The distance and direction from an origin.
Coplanar: Points and lines in the same place.
Deductive Reasoning: Reasoning logically from given facts to a conclusion.
Inductive Reasoning: Reasoning that reaches a conclusion based on a pattern.
Line: A series of points that extends in two opposite directions without an end.
Measure of an Angle: Angles are measured in degrees.
Midpoint: A point that divides a segment into two congruent segments.
Obtuse Angle: An angle whose measure is between 90 and 180 degrees.
Opposite Rays: Collinear rays with the same endpoint. They form a line.
Parallel Lines: Two lines that lie in the same plane but do not intersect.
Parallel Planes: Planes that do not intersect.
Perpendicular Bisector: A segment, ray, line or plane that is perpendicular to the segment at its midpoint.
Plane: A flat surface that extends in all directions without end; has no thickness; surface of a sphere.
Point: Location.
Postulate: An accepted statement of a fact.
Proof: A convincing argument that uses deductive reasoning.
Quadrant: What the x-axis and y-axis are divided into.
Ray: A part of a line consisting of one endpoint.
Right Angle: An angle whose measure is 90 degrees.
Segment: A part of a line consisting of two points (enpoints), and all points between them.
Segment Bisector: A line, segment, ray, or plane that intersects a segment at its midpoint.
Skew Lines: Two lines that don't lie on the same plane.
Space: The set of all points.
Straight Angle: And angle whose measure is 180 degrees.
Straight Edge: A ruler with no markings on it.
Supplementary Angles: Two angles are supplementary if the sum of their measures is 180 degrees.
Theorum: A conjecture that is proven a theorum.
Vertical Angles: The sides of two angles when they have opposite rays.