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• hydro
  hydro

  noun

  hydroelectric power.
• hydro-
  hydro-

  a combining form meaning “water,” used in the formation of compound words.
• Hydro
  Hydro

  noun

  (esp in Canada) a hydroelectric power company or board
• hydro–
  hydro–

  A prefix that means: “water” (as in hydroelectric) or “hydrogen,” (as in hydrochloride).

hydro

¹ American  

[hahy-droh] / ˈhaɪ droʊ /

noun

hydros plural

1. Informal. hydroelectric power.

2. Informal. hydroplane.

3. British.

   1. a bathhouse, hotel, or resort catering to people taking mineral-water health cures; spa.

   2. an establishment furnishing hydrotherapy.

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adjective

1. Informal. of, relating to, or furnishing water, water power, or hydroelectricity.

   funds for new hydro projects.

hydro- ² American  

1. a combining form meaning “water,” used in the formation of compound words.

   hydroplane; hydrogen.

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hydro- ³ American  

1. a combining form representing hydrogen in compound words, denoting especially a combination of hydrogen with some negative element or radical.

   hydrobromic.

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Hydro ¹ British  

/ ˈhaɪdrəʊ /

noun

1. (esp in Canada) a hydroelectric power company or board

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hydro ² British  

/ ˈhaɪdrəʊ /

adjective

1. short for hydroelectric

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noun

1. a Canadian name for electricity when it is supplied to a residence, business, institution, etc

hydro ³ British  

/ ˈhaɪdrəʊ /

noun

1. (esp formerly) a hotel or resort, often near a spa, offering facilities for hydropathic treatment

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hydro- ⁴ British  

combining form

1. indicating or denoting water, liquid, or fluid

   hydrolysis

   hydrodynamics

2. indicating the presence of hydrogen in a chemical compound

   hydrochloric acid

3. indicating a hydroid

   hydrozoan

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hydro– Scientific  

1. A prefix that means: “water” (as in hydroelectric) or “hydrogen,” (as in hydrochloride).

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Usage

What does hydro- mean? Hydro- is a combining form used like a prefix that has two distinct senses. The first of these senses is “water,” and this form of hydro- is often used in a variety of scientific and technical terms. Hydro- comes from Greek hýdōr, meaning “water.”The second of these senses is “hydrogen,” and this form of hydro- is occasionally used in a variety of scientific terms, especially in chemistry. Hydrogen, the lightest of the elements, combines with oxygen to form water. The word hydrogen comes from French hydrogène. The suffix -gen, or its equivalent in French, means "that which produces." Hydrogen literally translates to "that which produces water."What are variants of hydro-?When combined with words or word elements that begin with a vowel, hydro- becomes hydr-, as in hydrant. Want to know more? Read our Words That Use article on hydr-.

Other Word Forms

Noun Inflected Forms

• hydros
  plural

Etymology

Origin of hydro¹

1880–85; by shortening of compounds with hydro- ¹ ( cf. -o); hydro ( def. 4 ) hydro- ¹ analyzed as an adj.

Origin of hydro-²

< Greek, combining form of hýdōr water

Example Sentences

See Examples For:

hydro hydro- Hydro hydros

He thought solar, wind and hydro power would each present their own environmental problems.

From Salon ● Jun. 26, 2026

“I will advance renewable energy, import less foreign fuel and stop decommissioning of hydro and nuclear power. However, many current initiatives have unintended consequences, and my plan focuses on incentives, not mandates,” she said.

From Los Angeles Times ● May 1, 2026

The Labour run-government in Cardiff Bay called its new sector deal a "strategic partnership" with the industry "accelerating renewable deployment across onshore and offshore, wind, solar, marine and hydro".

From BBC ● Mar. 18, 2026

This is supported by record high hydro reserves—energy which hasn’t been sold yet—of 9 Terawatt hours.

From The Wall Street Journal ● Feb. 26, 2026

Mahipar—which means “Flying Fish”—was a high summit with a precipitous drop overlooking the hydro plant the Germans had built for Afghanistan back in 1967.

From "The Kite Runner" by Khaled Hosseini

By choosing certain spots, each species is hydro- and thermoregulating, Muñoz says.

From Science Magazine ● Sep. 22, 2022

The energy business would encompass equipment and services for gas, coal and wind turbines, hydro-, nuclear and electric power generation.

From Reuters ● Nov. 10, 2021

Solar projects accounted for 60 percent of the projects, while hydro- electric plants were 75 percent of new capacity.

From BusinessWeek ● Sep. 8, 2011

They are given names consisting of the prefix hydro-, the name of the second element present, and the termination -ic.

From An Elementary Study of Chemistry by McPherson, William

But enough of these follies: ‘Necro-, pyro-, geo-, hydro-, cheiro-, coscinomancy, With other vain and superstitious sciences.’

From Witch, Warlock, and Magician Historical Sketches of Magic and Witchcraft in England and Scotland by Adams, W. H. Davenport (William Henry Davenport)

But they were outplayed on Sunday as Australia cruised to a 66-47 win at The Hydro in Glasgow.

From BBC ● Jul. 26, 2026

The King's Baton was then paraded around the Hydro by swimmer Hannah Miley and para-cycling great Neil Fachie.

From BBC ● Jul. 23, 2026

The African nations led the way with Botswana the first to enter the Hydro.

From BBC ● Jul. 23, 2026

This year the event will be staged at the Hydro and will feature performances by headliner KT Tunstall, Callum Beattie, Nathan Evans, Tom Walker and Saint Phnx.

From BBC ● Jul. 22, 2026

“I want to put some dog pee in his fancy Hydro Flask.”

From "Finding Junie Kim" by Ellen Oh

Earlier, I was told the hydros hover 4 or 5 inches over the water.

From Seattle Times ● Aug. 5, 2023

Race the hydros, run the hidden ball trick — anything to remind us that making money will always be more important than winning baseball games.

From Seattle Times ● Apr. 27, 2018

The pirates are sober and nicer, the newer turbine-powered hydros are quieter and safer.

From Seattle Times ● Jul. 27, 2013

As in the case of big TVA it finally boiled down to how the PWA "hydros" could market their power.

From Time Magazine Archive

The Navy had two Wright-Burgess hydros and a few nondescripts.

From Jane's All the World's Aircraft 1913 by Various