| Ray | Directed line segment consisting of an endpoint and a direction. Notated as $\overrightarrow{EF}$, where $E$ denotes the endpoint and $F$ denotes a point along the ray. |
| Angle | Union of two rays with a common endpoint. Notated as $\angle DEF$ or $\angle FED$, where $D$ and $F$ are along the points of each ray, and $E$ is the vertex. $\angle EFD$ is not valid notation, because the vertex must be the middle. |
| $\theta$ | A lowercase theta is used to represent a (non right) angle in a triangle |
| $\phi$ | A lowercase phi is used to represent another unknown angle in a triangle. As an example, in an algebraic equation, $x$ might be used to represent the first unknown and $y$ the second. In trig, $\theta$ would |
