(N/A) Dimensional formula: The expression that shows how and which of the base quantities represent the dimensions of a physical quantity.
Density is defined as mass per unit volume: $\rho = \frac{M}{V}$.
Dimensional formula of mass is $[M^1 L^0 T^0]$.
Dimensional formula of volume is $[M^0 L^3 T^0]$.
Therefore,the dimensional formula of density is $\frac{[M^1 L^0 T^0]}{[M^0 L^3 T^0]} = [M^1 L^{-3} T^0]$.
Dimensional equation: An equation obtained by equating a physical quantity with its dimensional formula is called the dimensional equation of the physical quantity.
Thus,the dimensional equation for density is $[\rho] = [M^1 L^{-3} T^0]$.