hydro-1

1.
a combining form meaning “water,” used in the formation of compound words:
hydroplane; hydrogen.
Also, especially before a vowel, hydr-1 .
Origin
< Greek, combining form of hýdōr water

hydro-2

1.
a combining form representing hydrogen, in compound words, denoting especially a combination of hydrogen with some negative element or radical:
hydrobromic.
Also, especially before a vowel, hydr-2 .
British Dictionary definitions for hydro-

hydro-

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
Word Origin
from Greek hudōr water
Word Origin and History for hydro-

before vowels hydr-, word-forming element meaning "water," from Greek hydro-, comb. form of hydor "water" (see water (n.1)). Also sometimes a comb. form of hydrogen.

hydro- in Medicine

hydro- or hydr-
pref.

  1. Water; liquid: hydrocephalus.

  2. Hydrogen: hydrochloride.

hydro- in Science
hydro-  
A prefix that means: "water" (as in hydroelectric) or "hydrogen," (as in hydrochloride).