# Why lowering of vapour pressure is not a colligative property?

In my textbook, it is written that lowering of vapour pressure is not a colligative property but relative lowering of vapour pressure is a colligative property. But why is that? There is literally no explanation given in my textbook as to why this is true. Please someone explain. I am so confused. Please help. (By lowering of vapour pressure I mean $$P_{0} - P_{S}$$ where $$P_{0}$$ is the vapour pressure of pure solvent and $$P_{S}$$ is the vapour pressure of the solvent containing non-volative solute. Relative Lowering in Vapour Pressure means $$\frac{P_{0} - P_{S}}{P_{0}}$$).

• Could you clarify with respect to the difference between 'relative lowering' and 'lowering'? – Jon Custer May 6 at 18:27
• Consider reporting the whole sentences – Alchimista May 7 at 9:10