acute angle

an angle measuring less than 90º

angle bisector

a line that divides an angle into two equal parts

axiom

an accepted statement of fact, same as a postulate

bisect

to divide exactly in half

collinear points

all the points that lie on the same line

congruent angles

angles that have exactly the same measure of degrees; equal angles

congruent segments

line segments that are exactly the same length

coordinate

the x and y values (x, y) of a point on a coordinate plane

coplanar

all the points that lie on the same plane

line

a series of points extending in two opposite directions without end

obtuse angle

an angle measuring more than 90º

opposite rays

two collinear rays with the same endpoint, same as a line

parallel lines

coplanar lines that do not intersect

perpendicular bisector

a line that intersects another line at its midpoint and at a 90º angle

plane

a (virtual) flat surface that has no thickness

point

a location that has no size, usually represented by a dot named by a capital letter

postulate

an accepted statement of fact, same as an axiom

ray

an endpoint and all the points on a line on one side of the endpoint

right angle

an angle that measure exactly 90º

segment

the part of a line consisting of two endpoints and all the points between them

skew lines

noncoplanar lines; therefore they do not intersect

straight angle

and angle that measures exactly 180º