###
point

indicates location in space and has no size.

###
line

a series of infinite points that extends forever in opposite directions.

###
plane

a flat surface that extends infinately in all directions

###
parallel lines

two lines in the same plane that never intersect

###
angle

formed by two rays with a common endpoint called the vertex

###
right angle

an angle whose measure is exactly 90 degrees

###
straight angle

an angle whose measure is exactly 180 degrees, an angle that forms a straight line

###
vertex

where two rays have a common end point

###
ray

a part of a line with one endpoint and all the points of the line on one side of the endpoint

###
line segment

a finite portion of a line.

###
intersecting lines

two lines in the same plane that share a single point

###
skew lines

lines that do not exist in the same plane. They are neither intersecting or parallel

###
acute angle

an angle whose measure is less than 90 degrees

###
obtuse angle

an angle whose measure is greater than 90 degrees and less than 180 degrees

###
complementary angles

two angles whose combined measures add up to 90 degrees

###
adjacent angles

two angles that share a common ray (vertex and side) but have no interior points in common

###
vertical angles

two angles that are opposite each other when two lines intersect. also known as opposite angles

###
acute triangle

a triangle with 3 acute angles

###
obtuse triangle

a triangle with one obtuse angle

###
isosceles triangle

a triangle with at least 2 congruent sides

###
supplementary angles

two angles whose combined measures add to 180 degrees

###
congruent

identical, equal

###
right triangle

a triangle with one right angle

###
scalene triangle

a triangle with sides of different lengths

###
equilateral triangle

a triangle with 3 congruent sides

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