A vector accent notation indicating directed line segments or vectors with double-lined arrow above the text.
Examples
Vector notation in geometry
\Overrightarrow{AB} = \Overrightarrow{OB} - \Overrightarrow{OA}
Ray in geometric construction
\text{Ray } \Overrightarrow{PQ} \text{ extends infinitely in one direction}
Vector addition with directed line segments
\Overrightarrow{AB} + \Overrightarrow{BC} = \Overrightarrow{AC}