99: two important weather terms

relative humidity:

–noun

the amount of water vapor in the air, expressed as a percentageof the maximum amount that the air could

hold at the giventemperature; the ratio of the actual water vapor pressure to thesaturation

vapor pressure. Abbreviation: RH, rh

dew point:

–noun

the temperature to which air must be cooled, at a given pressureand water-vapor content, for it to reach saturation; thetemperature at which dew begins to form.