Common words:
* Hydrate: To combine with water. (e.g., "Drink plenty of water to stay hydrated.")
* Hydrant: A pipe with a valve that supplies water.
* Hydraulic: Relating to the use of water to transmit power. (e.g., "A hydraulic jack uses water pressure to lift heavy objects.")
* Hydroelectric: Generating electricity from water power. (e.g., "The dam provides hydroelectric power to the city.")
* Hydrogen: A colorless, odorless gas that is the lightest element.
* Hydrocarbon: A compound containing only carbon and hydrogen. (e.g., methane, propane)
* Hydrocephalus: A condition in which fluid builds up in the brain.
* Hydrophobia: Fear of water.
Scientific terms:
* Hydrophilic: Attracted to water.
* Hydrophobic: Repelled by water.
* Hydrometer: An instrument for measuring the specific gravity of liquids.
* Hydrolysis: The chemical breakdown of a compound by reaction with water.
* Hydrology: The study of water and its properties.
* Hydroplane: To skim over water at high speed.
These are just a few examples, and there are many more words with the "hydr-" prefix. If you come across a word with this prefix, you can usually guess its meaning based on the context and the Greek root "hydor."