Humidity denotes the moisture content of a gas or another substance. Humidity on the surface indicates wetness. Humidity in the air is able to hold a certain amount of water, depending on the temperature of the air. If moist air is cooled down, it will absorb and retain less water. Water condenses on the coolest surfaces. If the air is warmed up, the relative humidity will decrease. Humidity in the environment is in the electronic manufacturing industry not wanted, as it can lead to corrosion or to leakage currents.