Answer:
Hydro = water

Hydration is about the water levels in someone/something.

Dehydrated = not enough water

Rehydrate = to take in more water to compensate for water loss

So in essance, hydration is the proses where a HO- ion is added to another molecule.

Example adding OH to CH3CH3 to make CH3CH2OH, which is alcohol

The chemical union of H2O with another element.

First answer by JEK. Last edit by Alayzhon. Contributor trust: 20 [recommend contributor recommended]. Question popularity: 27 [recommend question].