Final answer:
Relative humidity is the ratio of vapor density to saturation vapor density, signifying the amount of water vapor present in the air relative to the maximum it can hold at a particular temperature.
Step-by-step explanation:
Relative humidity is defined as the ratio of the vapor density in the air to the saturation vapor density, which is the maximum amount of water vapor that the air can hold at a given temperature.
When the relative humidity is 100%, it means the air is fully saturated with water vapor and cannot hold any more, leading to no evaporation. The amount of water vapor air can contain increases with the air temperature - warm air can hold more moisture than cold air. Therefore, as the temperature rises, the capacity of air to hold water increases, which is why a blow dryer uses hot air to effectively dry wet hair more quickly due to increased evaporation rates.
Understanding the concept of relative humidity is essential in various scenarios, such as predicting weather patterns, calculating the dew point, and comprehending the comfort level in varying humidity conditions.