Refer to figure.
Relative Humidity is determined by both moisture content and temperature. It is expressed as a percentage and indicates how close the air is to saturation. For instance, if the relative humidity is 100%, the air is fully saturated with water vapor. If it is 50%, the air contains half the amount of water vapor needed for saturation. The relative humidity also varies with air temperature:

• As temperature rises, air can hold more water molecules. Therefore, if the amount of water vapor remains constant and the temperature increases, the relative humidity decreases.
• Conversely, colder air requires less moisture to reach saturation compared to warmer air, so a drop in temperature increases relative humidity.

The dew point is the temperature at which air becomes saturated with moisture. Dew point is a more reliable indicator of humidity than relative humidity because dew point is not affected by a change in air temperature and doesn’t fluctuate much throughout the day. Spread is the difference between the ambient temperature and the dew point temperature - a small spread means the air is nearly saturated. If the dew point remains constant and the temperature increases, the temperature-dew point spread increases.