### Best constant approximants in Orlicz-Lorentz spaces

The best constant approximant operator is extended from an Orlicz-Lorentz space ${\Lambda}_{w,\varphi}$ to the space ${\Lambda}_{w,{\varphi}^{\text{'}}}$, where ${\varphi}^{\text{'}}$ is the derivative of $\varphi $. Monotonicity property of its extension is established.