Geometry Terms

line A series of points that extends in two opposite directions without end.

Line segment Part of a line that has 2 endpoints.

Intersecting lines Lie in the same plane and have exactly one point in common.

ray A part of a line that has one endpoint.

point A location that has no size.

Parrallel lines Lines in the same plane that never intersect.

Plane A flat surface with no thickness that extends with no end in all directions on the surface.

Triangle A polygon with 3 sides.

Quadrilateral A polygon with 4 sides.

Pentagon A polygon with 5 sides.

Hexagon A polygon with 6 sides.

Heptagon A polygon with 7 sides.

Octagon A polygon with 8 sides.

Nonagon A polygon with 9 sides.

Decagon A polygon with 10 sides.

Right Angle An angle measuring ____.

Perpendicular Lines Lines that intersect to form right angles.

Vertex The point of intersection of two sides of an angle.

Degrees Angles are measured in units called degrees.

Acute Angle An angle with a measurement between ____ and ____.

Obtuse Angle An angle with a measurement between ____ and ______.

Straight Angle An angle with a measurement of ______.

Rectangular Prism A solid having two opposite ends that are parallel and are the same size and shaped as a rectangle. EX: shoe box, cereal box

Cube Rectangular prism whose sides are all squares. EX: dice

Triangular Prism A solid having two opposite sides that are parallel and are the same size and shaped as a triangle. *** BASES ARE TRIANGLES***

Cone A 3-dimensional figure with one circular base and one vertex. EX: ice cream cone, birthday hat

Cylinder A 3-dimensional figure with two congruent parallel bases that are circles. EX: cans of food, paper towel roll

Sphere A solid that has a boundary consisting of all points at a given distance from a point that is the center. EX: basketball, globe

Equilateral Triangle A triangle with 3 congruent sides.

Isosceles Triangle A triangle with 2 congruent sides.

Scalene Triangle A triangle with no congruent sides.