what is the difference between density and relative density of a substance

THUMS UP PLEASE

When you are talking about the mass by unit volume, it is called as density.

For eg. Density of water = 1000 kg m^-3
              Density of any other substance = x
 
Depending upon what the value of 'x' is, the other substance may sink / float.

But when you are 'comparing' the density of value of object x to the density of water, it is reffered to as relative density.

For eg. Density of any substance = 1000 kg m^-3
But, if    Density of water  = 1 kg m^-3,

Then acc. to the formula,
Relative Density = DENSITY OF THE OBJECT/DENSITY OF WATER

                               = 1000/1  = 1000

Since it is more than the 1, obviously it will sink.

This is the concept.

Hope it helps.
Cheers!
 

Density is defined as mass per volume. Density of a material is the amount of substance contained in unit volume of the material. SI unit of density is kg/m³.

Relative density is the ratio of density of a substance to the density of a reference material. Usually, the reference material is water. Relative density is also known as specific gravity.

Density:

The density of a substance is defined as mass of the substance per unit volume i.e

Density = Mass / Volume .

The SI unit of density is kg/m³

Relative Density:

The Relative Density of a substance is the ratio of its density to that of water. i.e

Relative Density = Density of substance / Density of water.

Relative Density is unitless.