hydro

UK: /ˈhaɪdrəʊ/ US: (hī′drō)

Inflections of 'hydro' (n): npl: hydros

WordReference Random House Unabridged Dictionary of American English © 2026

hy•dro  (hī′drō), n., pl. -dros for 2, 3, adj. 
n. 

1. Informal Terms hydroelectric power.
2. Informal Terms hydroplane.
3. British Terms
   • a bathhouse, hotel, or resort catering to people taking mineral-water health cures;
     spa.
   • an establishment furnishing hydrotherapy.

adj. 

4. Informal Terms of, pertaining to, or furnishing water, water power, or hydroelectricity:
   funds for new hydro projects.

• 1880–85; by shortening of compounds with hydro-¹ (compare -o); (def. 4) hydro-¹ analyzed as an adjective, adjectival

hydro-¹ ,

1. Chemistry a combining form meaning "water,'' used in the formation of compound words:
   hydroplane; hydrogen.

Also,[esp. before a vowel,] hydr- ¹.

• Greek, combining form of hýdōr water

hydro-² ,

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

Also,[esp. before a vowel,] hydr- ².

Collins Concise English Dictionary © HarperCollins Publishers::

hydro / ˈhaɪdrəʊ/ noun ( -dros)

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

hydro / ˈhaɪdrəʊ/ adjective

1. short for hydroelectric

noun

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

Collins Concise English Dictionary © HarperCollins Publishers::

Hydro / ˈhaɪdrəʊ/ noun

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

Collins Concise English Dictionary © HarperCollins Publishers::

hydro-, (sometimes before a vowel)hydr- 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

Etymology: from Greek hudōr water