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Line

A straight path that goes on forever in opposite directions.

Line Label

A label that is a line with arrows on both ends.

Ray

A part of a line that has one endpoint and extends without end in one direction.

Ray Label

A label that is a line with an arrow on one end

Angle

A figure formed by two rays or line segments with two endpoints.

Angle Lable

A label that is similar to a "less than symbol" only flat on the bottom.

Parallel

The same distance apart at every point.

Perpendicular

Lines, line segments, or rays are this if they form right angles.

Oblique Lines

Lines that are not parallel or perpendicular.

Protractor

A semicircular instrument for measuring and constructing angles.

Degree

A unit of measuring angles. Also a unit for measuring temperature.

Right Angle

An angle that measure 90 degrees.

Intersecting Lines

Lines that cross at the same point.

Complementary

Two angles whose sum of their measures is 90 degrees.

Supplementary

Two angles whose sum of their meaures is 180 degrees.

Acute

Angle greater than 0 degrees and less than 90 degrees.

Right Angle

A 90 degree angle.

Obtuse

Angle greater than 90 degrees and less than 180 degrees.

Straight Angle

A 180 degree angle.

Reflex Angle

Angle greater than 180 degrees and less than 360 degrees.

Circle

A shape that measures 360 degrees.

Counter-Clockwise

Left turn

Clockwise

Right turn

1 turn

90 degrees.

2 turns

180 degrees.

3 turns

270 degrees.

4 turns

360 degrees.

Quadrilateral

A two-dimensional figure with four sides.

Congruent

figures that are the same shape and size.

Polygon

A closed plane figure with sides made of straight line segments.

Vertical Angles

A pair of opposite angles formed by intersecting lines.

Opposite Angles

These angles are formed by two intersecting lines and have the same measure.

360 degrees

The sum of the interior angles of a quadrilateral.

180 degrees

The sum of the interior angles of a triangle.