Geometry Ch. 1 Vocab. (Lessons 1-2 to 1-5)

line

A line is represented by a straight path that extends in two opposite directions without end and has no thickness.

linear pair

A pair of adjacent angles whose non-common sides are opposite rays. HINT: linear pairs form supplementary angles (sum of 180 degrees)

plane

A plane is represented by a flat surface that extends without end and has no thickness. A plane contains infinitely many lines.

point

A point indicates a location and has no size.

segment bisector

A point, line, ray, or other segment that intersects a segment at its midpoint. A segment bisector splits a segment into two equal parts.

ray

A ray is part of a line that consists of one endpoint and all the points of the line on one side of the endpoint.

angle bisector

A ray that divides an angle into two congruent angles.

segment

A segment is part of a line that consists of two endpoints and all points in between.

angle

An angle is formed by two rays with the same endpoint.

straight angle

An angle whose measure is exactly 180 degrees.

right angle

An angle whose measure is exactly 90 degrees.

obtuse angle

An angle whose measure is greater than 90 degrees but less than 180 degrees.

acute angle

An angle whose measure is less than 90 degrees.

m<COD = 45

This is read "The measure of angle COD equals 45 degrees"

intersection

This is the point where two or more figures touch. Their intersection is the set of points the figures have in common.

supplementary angles

Two angles whose measures have a sum of 180 degrees.

complementary angles

Two angles whose measures have a sum of 90 degrees.

vertical angles

Two angles whose sides are opposite rays.

congruent angles

Two angles with the same measure.

adjacent angles

Two coplanar angles with a common side, a common vertex, and no common interior points.

congruent

Two segments or angles that have the same measure.

sides

The rays are the SIDES of the angle.

coplanar

These are points and lines that are on the same plane. All points of a line are coplanar.

collinear points

These are points that are on the same line.

postulate or axiom

These are rules that are accepted as true or fact.

opposite rays

These are two rays that share the same endpoint and form a line.

vertex

The endpoint is the vertex of the angle.

midpoint

The midpoint of a segment is a point that divides the segment into two congruent segments.