# Differential and its relation with derivative

*Differential of a function. Geometrical meaning of a differential.*

**
Differential of a function
**
is a product of a derivative

*f*’(

*x*

_{ 0 }) and an increment of argument :

*df*=

*f*’(

*x*

_{ 0 }) ·

*.*

Geometrical meaning of a differential is clear from Fig.2 : here
*
df
*
= CD