(N/A) Displacement: The distance of an oscillator (a body performing simple harmonic motion) at any instant from its equilibrium (fixed or reference) position is called the displacement of the oscillator at that instant.
The displacement is considered positive on one side of the equilibrium point and negative on the other side. In short,displacement can have zero,positive,or negative values.
Displacement refers to the change with time of any physical property under consideration. Its examples are as follows:
$(1)$ In the case of rectilinear motion of a steel ball on a surface,the distance from the starting point as a function of time is its position displacement. The choice of origin is a matter of convenience.
$(2)$ Consider a block of mass $m$ attached to a spring,the other end of which is fixed to a rigid wall,as shown in figure $(a)$. The block moves on a frictionless surface. The motion of the block can be described in terms of its distance or displacement $x$ from the wall.