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 in Canada) a hydroelectric power company or board

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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-.

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

Its 2025 performance was driven by record levels of biomass generation, pellet production and earnings from its hydro unit, they say.

From The Wall Street Journal • Feb. 27, 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

But climate change is hitting the region hard, triggering water shortages that hobble the vast Toktogul hydro power plant and lead to electricity shortages.

From Barron's • Nov. 30, 2025

Then there are long-established hydro power systems, whereby water is released from a higher reservoir to a lower one, also driving turbines.

From BBC • Sep. 10, 2025

The editor was still not hack from covering a plowing match; his mother said that the hydro maintenance crew covered a large area of the country...

From "The Incredible Journey" by Sheila Burnford