A reflection over line is a transformation in which each point of the original figure has an image that is the same distance from the reflection line as the original point, but is on the opposite side of the line.
Common Notations:
[tex]\begin{gathered} r_{x-axis}(x,y)=(x,-y)_{} \\ r_{y-axis}(x,y)=(-x,y)_{} \\ r_{y=x}(x,y)=(y,x)_{} \\ r_{y=-x}(x,y)=(-y,-x) \end{gathered}[/tex]