Hydro-, or hydr- before a vowel, is an English prefix that indicates either water (e.g. hydroelectric), liquid (e.g. hydrodynamics), or hydrogen (e.g. hydrochloride). The term comes from the Greek hudro-, hudr-, from hudōr (meaning water).

Hydro

• Hydro, a town in the U.S. state of Oklahoma
• "Hydro" as an adjective or noun, is sometimes used as a short form for hydroelectricity. In areas where hydroelectrical power is prevalent, such as Canada, it is essentially a synonym for "electricity services" or "mains."
  • Many Canadian provincial electricity companies have "hydro" in their name. (See hydroelectricity) They include:
    • BC Hydro in British Columbia
    • Hydro-Québec in Québec
    • Hydro One in Ontario
    • Hydro-Electric Power Commission of Ontario in Ontario
    • Manitoba Hydro in Manitoba
    • Newfoundland and Labrador Hydro in Newfoundland and Labrador
    • Canadian Hydro Developers in Ontario, Alberta and British Columbia
    • Municipal companies in these provinces often have "hydro" in their name, such as Toronto Hydro
  • Australian companies with "hydro" in their names include Snowy Hydro Limited and Hydro Tasmania
  • Norsk Hydro, a company in Norway
• Hydro, a hotel in a spa town at which guests may "take the waters."
• Hydro, a nickname for some types of cannabis, sometimes referred to as "dro." Generally these strains of cannabis are grown hydroponically
• Hydro, a nickname for the American professional wrestler Jamar Shipman
• Hydro, a slang nickname given to people who come from the Indian province of Hyderabad

Words derived from "hydro"

• Hydro Majestic Hotel, a hotel in Medlow Bath, New South Wales, Australia, located on a clifftop overlooking the Megalong Valley on the southern side of the Great Western Highway and noted for its unusual mix of architectural styles
• From the hydroelectricity context, a hydro corridor or hydro field is an open space through which high-voltage power lines pass

Entertainment

• HydroRacers, a mod by Stratactic Studio for various retail computer games
• Hydro-Man, a supervillain in Marvel Comics' universe. He is a frequent antagonist of Spider-Man and an occasional ally of The Sandman and the Frightful Four, and a member of the Masters of Evil
• Hydro Hog, a villain in Mighty Morphin Alien Rangers and the nemesis of the Aquitian Rangers. He was known as the Emperor of the Dark Waters on Aquitar for his evil way and was eventually defeated by the Shogun Megafalconzord

Science and technology

• Hydrobiology, in biology, the study of water and the water cycle
• Hydrocoral
• Hydrocolloids
• Hydrogeology, in geology, the study of groundwater and its occurrence, distribution, and effects
• Water cycle or hydrologic cycle
• Hydrograpy
• Hydrotherapy
• Hydrospace
• Hydrosphere
• Hydrostatics
• Hydrothorax
• Hydroxide

Specific chemical substances

• Hydrobromic acid
• Hydrocarbon
• Hydrochloric acid
• Hydrochloride
• Hydrochlorothiazide
• Hydrocortisone
• Hydrocyanic acid
• Hydrofloric acid
• Hydrogen
• Hydrogenase
• Hydrogen bromide
• Hydrogen chloride
• Hydrogen cyanide
• Hydrogen floride
• Hydrogen peroxide
• Hydrogen sulfide
• Hydrosulfate
• Hydrosulfide
• Hydrosulfite
• Hydrosulfurous acid
• Hydroxyapatite
• Hydroxyl
• Hydroxylamine
• Hydroxyurea