/sci/ - Science & Math

In physics when I have an equation,X(t),the first derivative dx/dt,give me the velocity,the second derivative is acceleration. Now my question is: wnhen i write the dv/dt ad then instead of the (v) I put dx/dt. this comes out as d^2x/(dt)^2
What does this mean? the "d^2x/(dt)^2" is it just a formality that this is a second derivative of X(t) function?