TERM
Point
Line
DEFINITION
Undefined term – a location
Undefined term – continues forever in both
directions
Intersecting Lines
When two lines cross – can only happen
at one point
Parallel Lines
Lines that do not intersect – parallel lines
have the same slope
Perpendicular Lines
Two lines that intersect to form right
angles (can also have perpendicular rays
and segments)
Ray
A part of a line that starts at a point (the
endpoint), and continues forever in one
direction
EXAMPLE
TERM
Line Segment
DEFINITION
A part of a line with two endpoints
Midpoint
The point on a segment that divides it into
two congruent segments
Angle
A figure formed by two rays (called sides)
with a common endpoint (called the
vertex)
Angle Bisector
A line or ray that divides the angle into two
congruent parts
Acute Angle
An angle that measures between 0 and 90
degrees
Obtuse Angle
An angle that measures between 90 and
180 degrees
EXAMPLE
TERM
Vertex
Equidistant
Circle
Arc
DEFINITION
The point where two segments, rays, or
lines meet.
Equal distance.
A set of points equidistant from the center.
A part of the circumference of a circle.
Plane
A flat surface on which a straight line
joining any two points on the plane would
entirely lie.
Distance
The numerical description of how far apart
objects are.
EXAMPLE
TERM
DEFINITION
Right Angle
An angle that measures 90 degrees
exactly
Straight Angle
An angle that measures 180 degrees
exactly
Complementary Angles
Two angles whose measures add up to
exactly 90 degrees
Supplementary Angles
Two angles whose measures add up to
exactly 180 degrees
Linear Pair
Two supplementary angles that share a
common vertex and a common side
Vertical Angles
Non-adjacent, non-overlapping angles
formed by two intersecting lines
EXAMPLE
TERM
Transversal
DEFINITION
A line that intersects two or more other
lines at different points
Corresponding Angles
Two angles that lie on the same side of a
transversal, in corresponding positions
with respect to the two lines that the
transversal intersects
Interior Angles
Given two (parallel) lines and a
transversal, any angle that lies “between”
the two (parallel) lines
Exterior Angles
Given two (parallel) lines and a
transversal, any angle does not lie
“between” the two (parallel) lines
Alternate Interior Angles
Two angles that lie on opposite sides of a
transversal between the two (parallel)
lines that the transversal intersects – they
do NOT form a linear pair
Alternate Exterior Angles
Two angles that lie on opposite sides of a
transversal not between the two (parallel)
lines that the transversal intersects
EXAMPLE