hydro-, hydra-, hydr-, hyd-

1. The study of the elasticity of fluids.
2. The elastic interaction between a body and the fluid in which it is immersed.

The conversion of water power into electric power.

1. A form of energy generated by the conversion of free-falling water to electricity.
2. The generation of electricity by using the motive power of water.
3. Relating to or producing electricity by the force of fast moving water; such as, rivers or waterfalls.

In many countries, hydroelectricity is the primary source of electrical power.

Galvanic stimulation of a portion of the body immersed in water.

Any volcanic explosion caused by a sudden generation of steam as, for example, when water comes in contact with hot lava or rock.

1. A winglike structure attached to the hull of a boat that raises all or part of the hull out of the water when the boat is moving forward, thus reducing drag.
2. A device consisting of a flat or curved piece (as a metal plate) so that its surface reacts to the water it is passing through: "The fins of a fish act as hydrofoils."
3. A boat equipped with hydrofoils.

1. The expulsion of water.
2. Shedding water, as with the hair of certain animals.
3. Describing the water-repellent hairs of certain aquatic insects; used for retaining a film of air.

Shedding water, as the cuticle (protective covering) of many insects.

A reference to galvanic stimulation to a portion of the body immersed in water.

1. A thick fluid like a jelly, formed by the addition of a substance to water.
2. A colloidal gel in which water is the dispersion medium.

Hydrogel is a network of polymer chains that are water-soluble, sometimes found as a colloidal gel in which water is the dispersion medium. Hydrogels are superabsorbent (they can contain over 99% water) natural or synthetic polymers.

Some uses for hydrogel include: disposable diapers that "capture" urine, or in sanitary towels, and for use with contact lenses (silicone hydrogels, polyacrylamides).

1. A colorless, odorless, flammable gas that combines chemically with oxygen to form water: the lightest of the known chemical elements.
2. A colorless, highly flammable gaseous element, the lightest of all gases and the most abundant element in the universe, used in the production of synthetic ammonia and methanol, in petroleum refining, in the hydrogenation of organic materials, as a reducing atmosphere, in oxyhydrogen torches, and in rocket fuels.
3. From 1791, French hydrogène, coined in 1787 by G. de Morveau from Greek hydr-, stem of hydros, "water" + French -gène, "producing". So called because it forms water when exposed to oxygen.

Source: water, most organic compounds. Use: industrial processes, production of ammonia, reduction of metal ores to metals.

The science dealing with the occurrence and distribution of underground water; hydrology; geohydrology: Hydrogeology studies the movement of subsurface water through rocks and the effect of moving water on rocks, including their erosion.

Hydrogeology is also concerned with the physical, chemical, and biological features of groundwater.

A plant that grows in earth and in water: One example of a hydrogeophyte is the Lucky Bamboo that can thrive in both soil and water.

A historical description of the earth's water surface.

1. An instrument for transmitting sound under water and recording messages so received.
2. A graph showing the variation of level, speed of flow, or another quantity at some point on a river.