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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