For questions relating to humidity. Humidity is the concentration of water vapor present in the air.

Humidity - A general term referring to the water content of a gas.

Source: https://doi.org/10.1351/goldbook.H02870

Relative Humidity - The ratio, often expressed as a percentage, of the partial pressure of water in the atmosphere at some observed temperature, to the saturation vapour pressure of pure water at this temperature.

Source: https://doi.org/10.1351/goldbook.R05267

IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997). Online version (2019-) created by S. J. Chalk. ISBN 0-9678550-9-8. https://doi.org/10.1351/goldbook.