Geometry Vocabulary/Definitions

Rectangle

A Quadrilateral with 4 sides and 4 right angles. Opposite sides are parallel.

point

A dot that specifies only location; it has no length, width, or depth. We usually represent a it with a dot on paper, but the dot we make has some dimension, while a true point has dimension 0. . B (point B)

Plane shape

A flat closed shape having only 2 dimensions.

Plane figure

A flat figure that can be closed or not closed.

Plane

A flat surface.

Symmetry

A plane figure that can be folded along a line so the two parts match.

Congruent

A plane figure with the same size and shape.

Circle

A polygon made with a continuous line which is always the same distance from the center.

Triangle

A polygon with 3 sides and 3 angles.

Quadrilateral

A polygon with 4 sides and 4 angles.

Parallelogram

A quadrilateral (4 sides & 4 angles) where opposites sides are parallel. (ie: Rectangle, square, rhombus, & diamond are parallograms)

Trapezoid

A quadrilateral (4 sides & 4 angles) with one pair of parallel sides.

Square

A quadrilateral with 4 equal sides and 4 right angles. Opposite sides are parallel.

Rectangular Prism

A solid shape that has: 6 faces (4 rectangles & 2 squares), 8 vertices (corners), and 12 equal edges.

Cube

A solid shape that has: 6 square faces all equal in size, 8 vertices (corners), and 12 equal edges.

Sphere

A solid shape that is perfectly round like a ball. No faces, edges, or vertices.

Cone

A solid shape with a circular base and a curved surface that come to a point (vertex).

Pyramid

A solid shape with a polygon as a base and triangular faces that come to a point (vertex or apex)

Cylinder

A solid shape with one curved surface and two congruent circular bases.

Line

A straight path that goes without end in two directions.

Isosceles Triangle

A triangle that has 2 equal sides.

Equilateral triangle

A triangle that has 3 equal sides.

Scalene Triangle

A triangle that has no equal sides. All 3 sides are different lengths.

Right Triangle

A triangle that has one right angle. It can also be an isosceles or scalene triangle.

Right Angle

An angle that is 90 degrees (It makes a square in the corner).

Side

Line segments of a polygon.

Ray

Part of a line that has one end point and goes in one direction without end.

Line Segment

Part of a line with two end points.

Volume

The amount of space occupied by a 3D object, measured in cubic units.

Perimeter

The distance around the figure.

Face

The flat surface of a 3D shape.

Line of Symmetry

The line that divides two matching parts. It can be vertical, horizontal, or diagonal.

Vertex

The point where two sides meet. (Shared end points of the line segments of a polygon.)

Area

The size a surface takes up, measured in square units.

Perpendicular Lines

Two lines that intersect to form right angles

Angle

Two rays with the same end point.

Edge

Where two surfaces join (intersect).

Rhombus

a parallelogram with four equal sides and equal opposite angles.