what is fundamental quantity.

I assume the question is about fundamental units  of given unit system.

 

For example in SI units , there are seven fundamental units related to fundamental physical quantitites.

 

These fundmental quantities are chosen in a unit suystem so that units of other quantities are expressed

in terms of units of these fundametal quantities. Units of fundamental quantities are called fundamental units .

 

Units derived from fundamental units to describe other quantities are called derived units.

 

Fundamental quantities and their respective units are tabulated below

 

Physical Quantity	Units
Length	m
mass	kg
time	s
current	A
temperature	K
amount of substance	mole
Luminious intensity	Cd