Basic Geometry Definitions
Terms in this set (23)
A point is undefined, but you can think of it as a location.
A line is undefined, but you can think of it as a series of points that extend in opposite directions without end.
A plane is undefined, but you can think of it as a flat surface with no thickness.
Collinear points lie on the same line.
Coplanar points lie on the same plane.
A line segment is the part of a line consisting of two points, called endpoints, and all points between them.
A ray is the part of a line consisting of one endpoint and all of the points of the line on one side of the endpoint.
Congruence is the quality or state of being exactly the same size and shape.
A vertex is the common endpoint of two line segments or rays.
An angle is formed by two rays or line segments with the same endpoint.
An acute angle is an angle whose measure is between 0 degrees and 90 degrees.
A right angle is an angle whose measure is exactly 90 degrees.
An obtuse angle is an angle whose measure is between 90 degrees and 180 degrees.
A straight angle is an angle that measures exactly 180 degrees.
A reflex angle is an angle that measures between 180 degrees and 360 degrees.
Two (or more) angles are complementary if their measures sum to 90 degrees.
Two (or more) angles are supplementary if their measures sum to 180 degrees.
A linear pair of angles is a pair of angles that are adjacent (share a side) and are supplementary.
Adjacent angles are two coplanar angles that have a common side and a common vertex but no common interior points.
Vertical angles are two angles whose sides form two pairs of opposite rays.
Two lines are parallel if they lie in the same plane and do not intersect.
Perpendicular lines are lines that intersect and form right angles.
Skew lines are two non-coplanar lines that do not intersect and are not parallel.