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vertex

The common endpoint of an angle

perpendicular

two lines that intersect to form right angles

parallel

lines that never intersect

ray

part of a line with one endpoint

line

extends forever in both directions

line segment

part of a line with two endpoints

acute angle

an angle that measures less than 90 degrees

obtuse angle

An angle that measures more than 90 degrees but less than 180 degrees

intersecting line

when 2 lines cross each other

right angle

an angle that measures exactly 90 degrees

straight angle

an angle that measures 180 degrees

perimeter

the distance around a figure.

vertical line

A line that goes up and down

horizontal line

a line that going from SIDE TO SIDE

area

the space inside a shape

symmetry

balance, same on both sides