Which instrument measures humidity?

• A. Barometer
• B. Hygrometer
• C. Thermometer
• D. Anemometer

Answer: (B)

Humidity is the amount of water vapor in the air, and it is measured with a hygrometer. Hygrometers detect changes in moisture in the air—some use materials like human hair that expand with rising humidity, while modern ones use electronic sensors that change electrical properties as humidity shifts. This information is essential for weather forecasting, comfort level assessments, and calculating dew point or frost risk. The other instruments measure different properties: a barometer tracks air pressure, which helps predict storms but doesn’t quantify moisture; a thermometer measures temperature; an anemometer measures wind speed. Because only a hygrometer directly measures water vapor in the air, it is the correct instrument for humidity.