What unit of measurement measures humidity?

Answer 1

humidity measures the amount of water vapor in the air.
Water concentration in air or water vapour.
The amount of water vapor in the air.
water vapor
moisture

Answer 2

Water vapor in the air is absolute humidity. The ratio of the absolute humidity to the maximum absolute humidity for that temperature and pressure is called the "relative humidity." Absolute humidity is very frequently expressed in terms of grains per pound of air, ppm, or vapour pressure. Relative humidity is usually expressed as a percent.
Relative humidity, expressed as a percentage from 0% to 100%, is the amount of moisture in air divided by the total possible amount of moisture in air. Unfortunately, the total possible amount changes when the temperature changes, so the relative humidity can change without adding or removing any water.

Another measure is dew point, which is the temperature at which water would condense. It doesn't change with temperature.

The lowest measured relative humidity in Phoenix, AZ, USA, is 2%--pretty dry. Sometimes the dew point is below 0 degrees, also pretty dry. (Celsius or Fahrenheit? Both!)

Answer 3

A humidity monitor measures humidity of places where humidity is critical for production of merchandise like medical supplies, medical equipment, and medication, etc.