What is the principle of superposition?

When two or more waves are acting simultaneously on the particle of the medium, the resultant displacement is equal to the algebraic sum of individual displacements of all the waves.
${\mathrm{y}}_{\text{net }}={\mathrm{y}}_1+{\mathrm{y}}_2+{\mathrm{y}}_3+\dots +{\mathrm{y}}_{\mathrm{n}}$