Vapor pressure is the amount of [pressure] which is exerted by the [vapor] [phase] of a [liquid] that has undergone some [evaporation].

When the [rate] of evaporation of the liquid into the vapor phase and the rate of [condensation] of the vapor back into the liquid phase are equal, the amount of pressure is called the equilibrium vapor pressure. A liquid which has no measurable vapor pressure (and barely [evaporate]s) is "nonvolatile." Vapor pressure (and [volatility]) increases with increasing [temperature].

The information in this writeup was taken from the [science] [dictionary] at http://biotech.icmb.utexas.edu/; [Lucy-S|I] oversaw the development of the [dictionary] (the website was mothballed in 1998) and I believe I wrote the entry this is based on.

vapor pressure (thing)