# Vocabulary (Geometry)

## 40 terms · Shapes and Solids

### point

An exact location in space.

### line

An endless straight path. Has no end points

### ray

Part of line that goes on forever in one direction. Has one end point.

### segment

Part of a line between two end points.

### plane

An endless flat surface. Defined by three points.

### angle

Formed by two rays with the same endpoint (vertex).

### right angle

An angle that measures 90 degrees.

### acute angle

An angle that measures less than 90 degrees.

### obtuse angle

An angle that measures more than 90 degress.

### straight angle

An angle that measures 180 degrees.

### parallel lines

Lines, in the same plane, that never intersect.

### Intersecting lines

Lines that intersect at any point.

### perpendicular lines

Lines that intersect at right angles.

### polygon

A closed, plane (flat) figure, formed by three or more line segments.

### regular polygon

A polygon that has sides of equal measure, and has angles of equal measure.

### triangle

3 sides, 3 angles

4 sides, 4 angles

### pentagon

5 sides, 5 angles

### hexagon

6 sides, 6 angles

### octagon

8 sides, 8 angles

### congruent

figures that have the same size and shape.

### similar

figures that have the same shape, but different sizes.

### line of symmetry

A line that divides a figure into two congruent parts.

### 180

Degrees in a triangle.

### polyhedron

A solid figure with faces that are polygons.

### prism

A polyhedron that has two congruent (exactly the same) bases.

### pyramid

A polyhedron with only one base.

### edge

Line where two faces come together.

### faces

The flat surfaces of solid figures

### vertex (vertices)

The point where several edges come together.

### transformation

Movement of a figure that does not change it's size or shape.

### translation

Sliding of a figure in a straight line. The figure does not change direction.

### reflection

Flipping a figure over a line (mirror). Figure is now in the opposite direction.

### rotation

Turning a figure around a point (vertex). Placing your finger on one corner of the figure, and turing the object around your finger.

### heptagon

7 sides, 7 angles.

### nanagon

9 sides, 9 angles.

### decagon

10 sides, 10 angles.

### 90

Degrees in a right angle.

### square

An equilateral parallelogram with one right angle.