Interpret Absolute Value Functions as Piecewise

If $y$ is the following piecewise function, where $k$ is a constant, what would $y$ be as an absolute value function? $$y = \bigg\{ \begin{array}{ccc} kx & \text{if} & kx \geq 0 \\ -kx & \text{if} & kx < 0 \end{array}$$