hydro-

¹ 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 ² 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- ³ American  

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

   hydroplane; hydrogen.

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hydro ¹ British  

/ ˈhaɪdrəʊ /

noun

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

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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  

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 ⁴ British  

/ ˈhaɪdrəʊ /

noun

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

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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-¹

< Greek, combining form of hýdōr water

Example Sentences

They do not include smaller-scale gas, biomass and hydro operators feeding in electricity at a local level, but these contribute a relatively small fraction of Britain's total generation.

From BBC

Its other favorite metals for 2026 are aluminum, where it recommends shares of Norsk Hydro, and lithium, where it likes Albemarle.

From Barron's

Based in Baltimore, the company is the largest producer of carbon-free energy in the U.S., with most of its output coming from hydro, wind, solar and nuclear.

From The Wall Street Journal

Many of their UK dates, including a performance at Glasgow's Ovo Hydro at the end of January, have sold out.

From BBC

In some cases like Spain, blessed with lots of sunshine, or Nordic countries, with abundant hydro power to provide energy when its wind farms fall silent, the transition looks promising.

From The Wall Street Journal