Vapor pressure is the pressure exerted by a vapor when condensation (<,>, or =) evaporation over its liquid in a closed system

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The equal sign (=) in this context means that the rate of condensation is equal to the rate of evaporation. In other words, when vapor pressure is in equilibrium with the liquid in a closed system, the amount of liquid evaporating is equal to the amount of vapor condensing back into the liquid phase. This balance between evaporation and condensation determines the vapor pressure of the substance.