# Pressure derivative of bulk modulus

Hi all what is the definition of pressure derivative of bulk modulus if it is a pressure derivative of bulk modulus at zero pressure. if the pressure is zero how it is derivative by pressure?

I guess the definition of derivative is still applicable: you take the limit of "modulus at pressure = $\triangle p$ minus modulus at pressure = 0" divided by $\triangle p$ for $\triangle p\rightarrow 0$.