Which pair of undefined terms is used to define a ray? line and plane plane and line segment point and line segment point and line

## Step 1<br />In geometry, there are certain terms that are not defined but are used to define other terms. These are known as "undefined terms". The undefined terms in geometry are point, line, and plane.<br /><br />## Step 2<br />A ray is a part of a line that has a starting point and extends infinitely in one direction. It is defined using the undefined term "point" and the defined term "line".<br /><br />## Step 3<br />Therefore, the pair of undefined terms used to define a ray is "point and line".