hydro

¹ American  

[hahy-droh] / ˈhaɪ droʊ /

noun

plural

hydros

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 /

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 ² British  

/ ˈhaɪdrəʊ /

noun

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

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Hydro ³ British  

/ ˈhaɪdrəʊ /

noun

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

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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-.

Etymology

Origin of hydro¹

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

Origin of hydro-²

< Greek, combining form of hýdōr water

Example Sentences

Much of that weak performance has to do with lower hydro generation, RBC’s Alexander Wheeler and Ziyad Jasimuddin write in a note.

From The Wall Street Journal • Mar. 18, 2026

In the pitch black of the mine, mud-splattered men with headlamps drill into the rock in two-man teams, using hydro drills with long, thin nozzles that shoot out pressurized water to loosen the ore.

From The Wall Street Journal • Jan. 27, 2026

"With the melting ice, you get the potential for hydro power in the area where the land is being exposed… so this presents itself as an interesting prospect."

From BBC • Jan. 23, 2026

Ecuador, a country of 17 million, relies on hydro generation for 70 percent of its electric power.

From Barron's • Jan. 22, 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