A ray is an important concept in geometry, and understanding how to identify a ray is key to understanding other more complex geometric concepts. In order for a ray to be identified, two undefined terms must be used. In this article, we will discuss what a ray is and what the two undefined terms are that are used to define it.

## Definition of a Ray

A ray is a geometric structure that consists of a line that has one endpoint and extends infinitely in one direction. It is often used to illustrate the concept of angles, and it is also used to measure distances. A ray is not the same as a line, because a line has two endpoints and extends infinitely in both directions.

## Identifying Undefined Terms

The two undefined terms used to define a ray are the endpoint and the direction. The endpoint is the starting point of the ray, and the direction is the line that the ray follows. The endpoint and the direction are both necessary in order to identify a ray.

In conclusion, a ray is an important concept in geometry and it is necessary to understand how to identify a ray. The two undefined terms used to define a ray are the endpoint and the direction. Once the endpoint and the direction are established, a ray can be identified.