Volume or cubical expansion -- " When a solid is heated and its volume increases, than expansion is called volume expansion or cubical expansion."
Let us consider a solid or liquid whose original is V0. When it is heated to a new volume, then the change in volume (ΔV) is directly proportional to (i) its original volume, v0 and (ii) increase in temperature ΔT.
where γ is called the coefficient of volume or cubical expansion.
Definition of γ : " It is defined as the increase in volume per unit volume per degree increase in temperature."
Unit of γ is °C-1 or K-1.