# Chapter 1 vocabulary

## 27 terms · Students will work in groups and individually to prepare for their vocabulary test.

a location

### line

made up of points and has no thicknessor width

### plane

flat surface made up of many points

### colinear

two or more points on the same line

### coplanar

points that lie on the same plane

### line segment

has a beginning and an end

### congruent

when shapes or segments have the same measurement

### midpoint

this is the point that is exactly between a segment

### segment bisector

when a segment, line, or plane intersets a segment at its midpoint

### bisector

to divide into to equal halves

### ray

Has a starting point but does not end

### angle

formed when two noncollinear rays that have a common endpoint

### vertex

the point shared by two rays

### right angle

angle that measures exactly 90 degrees

### acute angle

angle that measures greater than 0 and less than 90 degrees

### obtuse angle

angle that measures greater than 90 but less than 180 degrees

### angle bisector

when a ray divides an angle into two congruent angles

two angles that have a common vertex, a common side, but no comon interior points

### vertical angles

two nonadjacent angles form by two intersecting lines.

### complementary angles

two angles whose measures have a sum of 90 degrees

### supplementary angles

two angles whose measures have a sum of 180 degrees

### perpendicular lines

lines that form 90 degree angles ( right angles)

### polygon

closed figure whose sides are all segments

### concave

closed figure whose lines cross the interior

### convex

closed figure whose lines do not cross interior

### perimeter

sum of all the lengths of its sides ( segments)

### regular polygon

all sides in a polygon are the same