# Geometry Chapter 1

## 41 terms · Vocabulary words from McDougall Littell Geometry, Chapter 1.

### perimeter

The distance around a polygon

### equilateral

A polygon with all sides congruent

### equiangular

A polygon with all interior angles congruent

### regular

A polygon with all sides and all angles congruent

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

### dodecagon

A polygon with 12 sides

### n-gon

A polygon with n sides

### supplementary

Two angles whose measures add up to 180 degrees

### complementary

Two angles whose measures add up to 90 degrees

Two angles that share a vertex and a side
and have no common interior points

### straight angle

An angle that measures 180 degrees

### right angle

An angle that measures 90 degrees

### acute angle

An angle that measures between 0 and 90 degrees

### obtuse angle

An angle that measures between 90 and 180 degrees

### bisect

To divide into two congruent parts

On the same line

### coplanar

On the same plane

### polygon

Closed figure formed by line segments
called sides where each side intersects
two others, one at each endpoint.

### convex

Polygon such that no line
containing a side of the polygon
contains a point in the interior.

### concave

Polygon that is not convex.

### circumference

Distance around a circle

### diameter

The distance across a circle through the center

### midpoint

The point that divides a segment into two congruent segments

### bisector

A point, ray, line, segment, or plane that intersects a segment at its midpoint

### angle

Two rays with the same endpoint

### opposite rays

Two rays with the same endpoint, that lie on the same line and go in opposite directions

### line

Has one dimension and is represented with two arrowheads; extends without end

### segment

Part of a line defined by two endpoints

### ray

Part of a line, from one endpoint going in one direction without end

### point

Has 0 dimensions and is represented by a dot

### plane

Has 2 dimensions, extends without end