Geometry Basic Terms
Another word for "dot" that does not have length or width.
Point
Measures between 0° and 90°
Acute angle
The common endpoint of an angle.
Vertex
A polygon with three sides. The sum of its angles equals 180°.
A triangle
A straight segment that extends forever in both directions.
Line
Measures between 90° and 180°
Obtuse angle
Another name for the two rays that share an endpoint and form an angle.
Arms or sides
A polygon with four sides. The sum of its angles equals 360°.
A quadrilateral
A straight line that starts at its endpoint and extends forever in one direction.
Ray
Measures 90°. The lines or segments that meet at this angle are perpendicular.
Right angle
Two angles, which when added together equal 180°.
Supplementary angles
This shape has infinite lines of symmetry.
A circle
Two lines in the same plane with no common points.
Parallel Lines
Measures 180°
Straight angle
Two angles, which when added together equal 90°.
Complementary angles
A figure is _____________ if you can draw a straight line through it that divides the figure into identical halves.
Symmetric
Two rays with a common endpoint form this.
Angle
A full 360°
Complete turn
When a line crosses two parallel lines you can find many equal angles. The angles opposite each other are called...
Vertical angles
A shape with more than three sides. The sum of its angles is
(n - 2) x 180
Polygon of n sides