Every material in made up of intensive or extensive property. Intensive property of a system does not depend on the system size or the amount of material in the system. But extensive property on the other hand depends on the amount of material present in the system.
Examples of intensive properties include temperature, density, vapor pressure and viscosity.
Assuming that there is some residual liquid left after equilibrium is reached, no matter how much liquid is present, at any given temperature, the vapor pressure will be the same because it is an intensive property.
