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hydrogenate to treat or cause to combine with hydrogen.
hydrogen bomb an extremely powerful bomb whose destructive energy comes from the fusion of hydrogen nuclei under intense heat and pressure, forming helium nuclei.
hydrogen ion the positive ion of a hydrogen atom whose electron has been removed, as in acids.
hydrogen peroxide an unstable compound of hydrogen and oxygen whose water solution is used mostly as an antiseptic or bleach.
hydrogen sulfide a poisonous, colorless gas that has the odor of rotten eggs and is used mostly in chemical manufacturing and metallurgy.
hydrography the study or science of describing or mapping the earth's bodies of water, esp. in relation to navigational or commercial uses.
hydroid characteristic of the asexual hydrozoan polyp. [2 definitions]
hydrolysis the decomposing of a chemical compound by combining it with water or the elements of water.
hydrolyte a substance that has gone through the process of hydrolysis.
hydrolyze to subject to or undergo hydrolysis.
hydrometer an instrument, usu. a sealed glass tube containing a graduated scale and weighted at one end, used to measure the specific gravity of liquids.
hydropathy the treatment of disease by the use of water, as by drinking or external application. (Cf. hydrotherapy.)
hydrophobia a deadly viral disease of the central nervous system, usu. transmitted by the bite of an infected animal; rabies. [2 definitions]
hydrophyte a plant that grows in water alone or in esp. wet ground.
hydroplane a light, fast motorboat that at high speeds skims the water with only the rear part of the hull touching the surface. [5 definitions]
hydroponics (used with a sing. verb) the growing of plants in nutrient solutions rather than in soil.
hydropower electrical energy from hydroelectric generating plants.
hydrosphere collectively, all bodies and forms of water on or around the earth's surface, including vapor and clouds in the atmosphere.
hydrostatics (used with a sing. verb) the scientific study of liquids at rest, esp. with regard to pressure and equilibrium.
hydrotherapeutics (used with a sing. verb) the practice or process of hydrotherapy.
hydrotherapy the treatment of disease through the internal or external application of water.