Advertisement Upgrade to remove ads


names a location and has no size


a straight path that has no thickness and extends forever


a flat surface that has no thickness and extends forever


points that lie on the same line


points that lie on the same plane


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


a point at one end of a segment or the starting point of a ray


a part of a line that starts at an endpoint and extends forever in one direction

Opposite rays

two rays that have a common endpoint and form a line

Postulate (axiom)

a statement that is accepted as true without a proof.


a point that corresponds to one and only one number on the ruler


the absolute value of the difference of the coordinates

Congruent Segments

segments that have the same length


a way of creating a figure that is more precise


the point that bisects, or divides the segment into two congruent segments



Segment Bisector

any ray, segment, or line that intersects a segment at its midpoint.


a figure formed by two rays, or sides, with a common endpoint called a vertex


an angle's common endpoint

Interior of an angle

the set off all points between the sides of the angles

Exterior of an Angle

the set of all points outside the angle

Acute Angle

an angle that measures grater than zero degrees and less than ninety degrees

Right angle

an angle that measures ninety degrees

Obtuse Angle

an angle that measures grater than ninety degrees and less than one-hundred-eighty degrees

Straight Angle

an angle formed by two opposite rays and measures one-hundred-eighty degrees

Congruent Angles

angles that have the same measure

Angle Bisector

a ray that divides an angle into two congruent angles

Adjacent Angles

two angles that are in the same plane with a common vertex and a common side, but no common interior points

Linear Pair

a pair of adjacent angles whose non-common sides are opposite rays

Complementary Angles

two angles whose measures have a sum of ninety degrees

Supplementary Angles

two angles whose measures have a sum of one-hundred-eighty degrees

Vertical Angles

two nonadjacent angles formed by two intersecting lines


the sum of the side lengths of the figure


the number of non-overlapping square units of a given size that exactly covers the figure


any side of a triangle


a segment from a vertex that forms a right angle with a line containing the base


a segment that passes through the center of the circle and whose endpoints are on the circle


a segment whose endpoints are the center of the circle and a point on the cicle


the distance around the circle


ratio of a circle's circumference to its diameter (3.14)

Coordinate Plane

a plane that is divided into four regions by a horizontal line


in a right angle triangle, the two sides that form the right angle


the side across from the right angle that stretches from one leg to the other


a change in the position, size, or shape, of a figure


the original figure


a figure after transformation


a transformation across a line. Each point and its image are exactly the same distance from the line


a transformation about a point. Each point and its image are the same distance from that point


a transformation in which all the points of a figure move the same distance, in the same direction

Please allow access to your computer’s microphone to use Voice Recording.

Having trouble? Click here for help.

We can’t access your microphone!

Click the icon above to update your browser permissions above and try again


Reload the page to try again!


Press Cmd-0 to reset your zoom

Press Ctrl-0 to reset your zoom

It looks like your browser might be zoomed in or out. Your browser needs to be zoomed to a normal size to record audio.

Please upgrade Flash or install Chrome
to use Voice Recording.

For more help, see our troubleshooting page.

Your microphone is muted

For help fixing this issue, see this FAQ.

Star this term

You can study starred terms together

NEW! Voice Recording