Meteorological definition “Humidity” of air refers to which of the following physical properties?

Introduction / Context:
Humidity is a fundamental atmospheric variable used in weather forecasting, comfort indices, and evaporation estimation. It characterizes how much water vapour is present in air.

Given Data / Assumptions:

• No specific units are provided; humidity can be expressed as absolute humidity, specific humidity, or relative humidity.

Concept / Approach:
Humidity quantifies the water vapour content. Relative humidity, the most common measure, is the ratio of actual vapour pressure to saturation vapour pressure at the same temperature, expressed as a percentage.

Step-by-Step Solution:

Verification / Alternative check:
Psychrometric relationships link humidity to wet-bulb/dry-bulb temperatures and dew point; these are all moisture-content indicators.

Why Other Options Are Wrong:
Temperature, pressure, and volume affect humidity but are not themselves humidity. Density alone does not define vapour content.

Common Pitfalls:
Confusing relative humidity with absolute moisture content or mixing temperature effects without distinguishing the definition.

Final Answer:
Moisture content of the air