##### Geometry Vocabulary Terms with Pictures

6th grade, 7th grade, 8th grade, 9th grade, 10th grade, 11th grade, 12th grade, College: First year, College: Second year

Point

An exact location in space, usually represented by a dot

Angle

A figure formed by two rays that have a common endpoint

Vertex

The point where two or more rays meet; the point of intersection of two sides of a polygon; the point of intersection of three or more edges of a solid figure; the top point of a cone; the plural of vertex is vertices

Circle

A closed plane figure with all points on the figure the same distance from the center

Radius

A line segment with one endpoint at the center of a circle and the other endpoint on the circle

Obtuse Triangle

A triangle that has one obtuse angle

Polygon

A closed plane figure formed by three or more line segments

Square

A rectangle with 4 equal sides

Pentagon

A polygon with five sides

Line

A straight path in a plane that goes on forever in opposite directions

Right Angle

An angle formed by perpendicular lines, line segments, or rays and with a measure of 90°

Parallel Line

Lines in a plane that never intersect

Circumference

The distance around a circle

Triangle

A polygon with three sides

Equilateral Triangle

A triangle with three congruent sides

Parallelogram

A quadrilateral whose opposite sides are parallel and congruent

Trapezoid

A quadrilateral with one pair of parallel sides

Closed Figure

A figure that begins and ends at the same point

Line Segment

A part of a line that includes two points, called endpoints, and all of the points

Acute Angle

An angle that has a measure less than a right angle (less than 90°)

Perpendicular Lines

Two lines that intersect to form four right angles

Chord

A line segment with its endpoints on a circle

Right Triangle

A triangle with one right angle

Isosceles Triangle

A triangle with two congruent sides

Quadrilateral

A polygon with four sides

Hexagon

A polygon with six sides and six angles

Ray

A part of a line, with one endpoint, that continues without end in one direction

Obtuse Angle

An angle whose measure is greater than 90° and less than 180°

Intersecting Lines

Lines that cross at exactly one point

Diameter

A line segment that passes through the center of

a circle and has its endpoints on the circle

Acute Triangle

A triangle in which all three angles are acute

Scalene Triangle

A triangle with no congruent sides

Rectangle

A parallelogram with four right angles

Octagon

A polygon with eight sides