what's humidity ?

moistness, dampness

http://dictionary.reference.com/browse/humidity

Humidity is the concentration of water vapour present in the air. Water vapor, the gaseous state of water, is generally invisible to the human eye. Humidity indicates the likelihood for precipitation, dew, or fog to be present.

Humidity refers to the amount of moisture or water vapor present in the air. It is an important factor when it comes to understanding and predicting weather patterns. Humidity is usually measured as a percentage and can affect how comfortable or uncomfortable the air feels.

To understand humidity, you need to measure two important components: the actual amount of water vapor in the air (known as absolute humidity) and the maximum amount of water vapor the air can hold at a particular temperature (known as the saturation point). The ratio of the actual amount to the maximum amount is what determines the humidity level.

There are different ways to measure humidity, but the two most common methods are relative humidity and dew point. Relative humidity is the ratio of the actual amount of water vapor to the maximum amount at a specific temperature, expressed as a percentage. Dew point, on the other hand, is the temperature at which the air becomes saturated and moisture starts to condense to form dew, fog, or clouds.

Weather instruments such as hygrometers are used to measure humidity levels. These instruments work by detecting changes in the electrical conductivity or the capacitance of the air, which varies with humidity.

Knowing the humidity level is significant because it affects our comfort, health, and the overall weather conditions. High humidity can make the air feel muggy and can contribute to heat-related illnesses, while low humidity can lead to dry skin, irritated respiratory systems, and static electricity.

Meteorologists and weather forecasters use humidity data to predict and analyze weather patterns, as high humidity is often associated with storm development and moisture availability.

So, to summarize, humidity refers to the amount of moisture in the air and can be measured using various methods such as relative humidity and dew point. It affects our comfort, health, and weather conditions and is an essential factor in meteorology.