Akademik

hydr-
combining form or hydro-
Etymology: alteration (influenced by Latin hydr-, hydro-) of Middle English ydr-, ydro-, from Old French ydr- & Middle French ydro-, from Latin hydr-, hydro-, from Greek, from hydōr — more at water
1.
a. : water

hydrogel

hydroelectricity

b. : hydraulic

hydropress

2. : water-loving organism — chiefly in generic names

Hydracarina

Hydrodictyon

3.
a. : hydrogen : containing hydrogen

hydriodic acid

hydroborate

b. now usually hydro- : combined with hydrogen — especially in names of organic compounds

hydroquinidine

c. : combined with water by hydration

hydracrylic acid

or by hydrolysis

hydrocellulose

4. : characterized by an accumulation of fluid in a (specified) bodily part

hydronephrosis

5.
a. : combined with water — in names of minerals

hydrohetaerolite

b. : characterized by addition of water or its constituents — in names of varieties of minerals

hydromica

6. [New Latin, from Hydra (genus of polyps)] : hydroid

hydromedusa

hydrorhiza

* * *

hydr-1
var. of hydro-1 before a vowel: hydrant.
hydr-2
var. of hydro-2 before a vowel: hydride.

* * *

hydr-,
combining form. the form of hydro- (Cf. ↑hydro-) before vowels, as in hydrant.

* * *

comb. form variant spelling of hydro- shortened before a vowel (as in hydraulic)

* * *

hydr-
the usual form of hydro- bef. a vowel.

Useful english dictionary. 2012.