# 1.1: The Building Blocks of Geometry

## 9 terms

### undefined terms

most basic figures of geometry: points, lines and planes

### points

shown as dots, have no size, named by capital letters such as A or X

### lines

have no thickness, are perfectly straight, and extend forever, can be named by two points on the line, with the double headed arrow over the two letters or by a single lowercase letter

### planes

extend indefinitely in all directions along a flat surface, can be represented by a piece of paper or white boards in the classroom, named by three points that lie in the plane, but are not all on the same line or by a script capital letter such as R

### collinear

points are contained by a single line

### coplanar

points are contained by a single plane

### segment

is part of a line that begins at one point and ends at another. the points are called endpoints of the segment

### ray

part of a line that starts at a point and extends infinitely in one direction, the point is called the endpoint

### angle

a figure formed by two rays with a common endpoint, the common endpoint is called the vertex, and the rays are the sides. It divides a plane into two regions, the interior and exterior