Psychrometrics

The branch of physics dealing with the properties of moist air — temperature, humidity, dew point and volume, and how they relate to each other.

Psychrometrics is the science behind why humidity, temperature and dew point are all connected rather than independent numbers. It explains why cooling air raises its relative humidity even with no moisture added (see relative humidity), why a dehumidifier's cold coil condenses water (see dew point), and why extraction performance changes with ambient temperature (see desiccant vs refrigerant).

You don't need the underlying physics to use a dehumidifier correctly, but it's the reason sizing isn't just "floor area in, capacity out" — volume, dampness, climate and usage pattern all interact the way psychrometric theory predicts, which is exactly what our sizing method accounts for.