Undefined and Defined Terms

• Point - something having a specific location but does not have dimensions, magnitude, or direction. A dot is used to represent this term.
• Line - a collection of an infinite number of points that extends infinitely in both directions. It has infinite length but no thickness or width.
• Plane - a set of points contained in a flat surface and extends indefinitely in all directions. It has length and width but no thickness.
• Collinear points - points that lie on the same line.
• Coplanar points - points that lie on the same plane.
• Line segment - a part of a line consisting of two endpoints and all the points between them.
• Ray - part of a line that has one endpoint and extends infinitely in one direction.
• Midpoint of a segment - a point on the line segment that divides it into two equal parts or segments.
• Congruent segments - two segments having the same measure or length.
• Segment bisector - it cuts the line segment into two equal parts.
• Betweenness - a mathematical concept that identifies the quality of a point between two other points on the same line.
• Perpendicular bisector of a segment - it is a segment, ray, or line that is perpendicular to a segment at its midpoint. Two lines are perpendicular if they form 90-degree angles.
• Angle - the union of two noncollinear rays with a common endpoint called vertex. Two rays are the sides of the angle.
• Congruent angles - the measure of the angles are equal.
• Angle bisector - divides the angle into two congruent angles.
• Right angle - is an angle with a measure of 90-degrees.
• Acute angle - an angle with a measure of greater than 0 but less than 90-degrees.
• Obtuse angle - is an angle with a measure of more than 90 degrees but less than 180 degrees.
• Adjacent angles - two angles with a common vertex, a common side and no common interior points.
• Complementary angles - two angles whose sum of the measure is 90 degrees. It may be adjacent or non-adjacent.
• Supplementary angles - two angles whose sum of the measure is 180 degrees. It may be adjacent or non-adjacent.
• Linear pair - two angles form this term if and only if they are adjacent and the non-common sides form a straight line.
• Vertical angles - a pair of non-adjacent angles formed by two intersecting lines.
• Transversal line - a line that intersects two or more coplanar lines at two or more distinct points.
• Alternate interior angles - two nonadjacent interior angles on opposite sides.
• Alternate exterior angles - two non-adjacent exterior angles on opposite sides of the transversal.
• Corresponding angles - two non-adjacent angles, one exterior and one interior on the same side of the transversal.
• Same side interior angles - two non-adjacent interior angles on the same side of the transversal.
• Same side exterior angles - two non-adjacent exterior angles on the same side of the transversal.