Hydrangeaceae Hydrangeaceae is a Family of flowering plants in the order Cornales, with a wide distribution in Asia and North America, and locally in southeastern Europe. In its broad sense, the family includes 17 genera, but some botanists divide the family into two, with seven genera split off into a separate family Philadelphaceae.
	Hydraulic ram A hydraulic ram is a water-powered cyclic pump. It harnesses the forces of water hammer to pump a portion of the water being used to power the pump to a point higher than where the water originally started. It is sometimes used in remote areas, where the right conditions exist, since it requires no outside source of Power other than the kinetic energy of falling water.
	Hydraulics Hydraulics is a science and engineering subject dealing with the mechanical properties of liquids. Hydraulics is part of the more general discipline of fluid power. The word "hydraulics" originates from the Greek language word ' which in turn orginates from ' meaning water organ which in turn comes from ' and ' .
	Hydrazine Hydrazine is the chemical compound with chemical formula Nitrogen2Hydrogen4. This species is widely used in chemical synthesis. It is perhaps best known as a component in rocket fuel. Hydrazine is also found in tobacco products.
	Hydrazoic acid Hydrazoic acid is a colorless, volatile, and extremely explosive liquid at room temperature and pressure.
	Hydrilla Hydrilla is an aquatic plant, native to cool to warm waters of Asia, Europe, Africa and Australia. Plants may be monecious or dioecious and can Vegetative reproduction by fragmentation and by tubers and turions. Stems branch near water surface.
	Hydrobromic acid Hydrobromic Acid is formed by dissolving the diatomic molecule hydrogen bromide in water. It has a Acid dissociation constant of −9, making it a stronger acid than hydrochloric acid, but not as strong as hydroiodic acid. Hydrobromic acid is one of the strongest mineral acids known.
	Hydrocarbon In chemistry, a hydrocarbon is any chemical compound that consists only of the elements carbon and hydrogen . They all contain a carbon backbone, called a carbon skeleton, and have hydrogen atoms attached to that backbone. Most hydrocarbons are combustible.
	Hydrocharis Hydrocharis is a genus of aquatic plants within the family Hydrocharitaceae. The best known species is Hydrocharis morsus-ranae, commonly called common or European frogbit, and occasionally water-poppy. It is a small floating plant resembling a small water lily. It has submerged roots, and bears small green and white flowers.
	Hydrocharitaceae Hydrocharitaceae is a plant family that includes a number of species of aquatic plant, broadly called the Tape-grasses, and includes the well known Canadian Waterweed and Frog's Bit. This familt includes both fresh and marine aquatics. They are found throughout the world in a wide variety of habitats, but are primarily tropical.
	Hydrochloric acid The chemical compound hydrochloric acid is the aqueous solution of hydrogen chloride gas. It is a strong acid, the major component of gastric acid and of wide industrial use. Hydrochloric acid should only be handled with appropriate safety precautions because it is a highly corrosive liquid.
	Hydrochlorothiazide Hydrochlorothiazide , sometimes abbreviated HCT, HCTZ, or HZT is a popular diuretic drug that acts by inhibiting the kidney's ability to retain water. This reduces the volume of the blood, decreasing peripheral vascular resistance.
	Hydrodynamics Hydrodynamics is fluid dynamics applied to liquids, such as water, alcohol, petroleum, and blood. . Blaise Pascal in the 1600s contributed some of the initial theory to this field. The term originates from the work of Daniel Bernoulli, based on the title of his work called Hydrodynamica .
	Hydroelectricity Hydroelectricity is electric power obtained from hydropower. Most hydroelectric power comes from the potential energy of dammed water driving a water turbine and electrical generator. Less common variations make use of water's kinetic energy or undammed sources such as tidal power.
	Hydrofluoric acid Hydrofluoric acid is a highly corrosive solution of hydrogen fluoride in water. Gaseous hydrogen fluoride is sometimes called anhydrous hydrofluoric acid. Hydrofluoric acid is a very toxic and corrosive acid. Perhaps confusingly, it is considered a weak acid because of its low tendency to dissociate to ions in water.
	Hydrofoil A hydrofoil is a boat with wing-like airfoils mounted on struts below the hull . As the craft increases its speed the hydrofoils develop enough lift for the boat to become foilborne - i.e. to raise the hull up and out of the water. This results in a great reduction in drag and a corresponding increase in speed.
	Hydrogen |- | Triple point || 13.8033 K, 7.042 kPa Hydrogen is a chemical element in the periodic table that has the symbol H and atomic number 1. At standard temperature and pressure it is a colorless, odorless, nonmetallic, Valence , tasteless, highly combustion diatomic gas .
	Hydrogen atom A hydrogen atom is an atom of the chemical element hydrogen. It is composed of a single negatively-charged electron circling a single positively-charged proton which is the Atomic nucleus of the hydrogen atom. The electron is bound to the proton by the Coulomb force.
	Hydrogen bond In chemistry, a hydrogen bond is a type of attractive intermolecular force that exists between two partial charge electric charges of opposite polarity. Although stronger than most other intermolecular forces, the typical hydrogen bond is much weaker than both the ionic bond and the covalent bond.
	Hydrogen bromide Hydrogen bromide is the diatomic molecule HBr. Under standard conditions, HBr is a gas, but it can be liquified. The aqueous solution hydrobromic acid forms upon dissolving HBr in water. Conversely, HBr can be liberated from hydrobromic acid solutions upon the addition of a dehydration agents.
	Hydrogen chloride Hydrogen chloride, also known under the name HCl, is a highly corrosive and toxic colorless gas that forms white fumes on contact with humidity. These fumes consist of hydrochloric acid which forms when hydrogen chloride Solution in Water. Hydrogen chloride gas as well as hydrochloric acid are important chemicals in chemistry, science, technology, and industry.
	Hydrogen cyanide Hydrogen cyanide is a chemical compound with chemical formula HCN. A solution of hydrogen cyanide in water is called hydrocyanic acid or Prussic acid. Pure hydrogen cyanide is a colorless, very poisonous, and highly volatility liquid that boiling slightly above room temperature at 26 Celsius, thereby generating hydrogen cyanide gas.
	Hydrogen fluoride Hydrogen fluoride is the chemical compound with the formula HF. It is the only fluoride of hydrogen. HF boils just below room temperature whereas the other hydrogen halides condense at much lower temperatures. This difference is attributed to the strong hydrogen bonding between HF molecules.
	Hydrogen iodide Hydrogen iodide is a diatomic molecule. Aqueous solutions of HI are known as hydroiodic acid or hydriodic acid, a strong acid. Hydrogen iodide and hydroiodic acid are, however, different chemical compounds: one is a gas at room temperature, the other is an aqueous solution.
	Hydrogen peroxide Hydrogen peroxide is a very pale blue liquid which appears clear in a dilute solution, slightly more viscous than water. It has strong oxidation properties and is therefore a powerful bleaching agent that has found use as a disinfectant, as an oxidizer, and in rocketry , and in bipropellant systems.
	Hydrogen sulfide Hydrogen sulfide, H2S, is a colorless, toxic, flammable gas that is responsible for the foul odor of rotten eggs and flatulence. It often results when bacteria break down organic matter in the absence of oxygen, such as in swamps, and sewers. It also occurs in volcano gases, natural gas and some well waters.
	Hydrography Hydrography focuses on the measurement of physical characteristics of waters and marginal land. In the generalized usage, "hydrography" pertains to measurement and description of any waters. With that usage oceanography and limnology are subsets of hydrography. In specialized usage the term applies to those measurements and descriptions of navigable waters necessary for safe navigation of vessels.
	Hydrology Hydrology is the study of the movement, distribution, and quality of water throughout the Earth, and thus addresses both the hydrologic cycle and water resources. A practitioner of hydrology is a hydrologist, working within the fields of either earth science or environmental science, physical geography or civil engineering and environmental engineering.
	Hydrolysis Hydrolysis is a chemical reaction or process in which a molecule is split into two parts by reacting with a molecule of Water , which has the chemical formula Hydrogen2Oxygen. One of the parts gets an OH- from the water molecule and the other part gets an H+ from the water.
	Hydromancy Hydromancy is the art of Crystal gazing by means of water, including the color, ebb and flow, or ripples produced by pebbles dropped in a pool. The Jesuit M. A. Del Rio described several methods of hydromancy. The first method described depicts a ring hanging by a string that is dipped into a vessel of water which was shaken.
	Hydrometer ory:Measuring instruments]] Category:Laboratory equipment Category:Laboratory glassware Category:Wet chemistry cs:Hustomer de:Arometer es:Densmetro mk:????????? nl:Hydrometer pl:Areometr sl:Areometer sr:????????? fi:Areometri sv:Hydrometer vi:Ph k?
	Hydromorphone Hydromorphone is a medication used to relieve moderate to severe pain. Hydromorphone is known by the trade name "Dilaudid", though an extended-release version called Palladone SR was available for a short time before being pulled from the market in July 2005 due to a high overdose potential when taken with alcohol.
	Hydronephrosis Hydronephrosis is distention and dilation of the renal pelvis, usually caused by obstruction of the free flow of urine from the kidney.
	Hydrophyllaceae The Hydrophyllaceae, or waterleaf family, are a family of flowering plants. Their taxonomic position is somewhat uncertain. Traditionally, and under the Cronquist system, they were treated as part of the order Solanales, as shown in the table at the right.
	Hydrophyllum The genus Hydrophyllum includes several herbaceous perennials including the Dwarf Waterleaf, or Ball-Headed Waterleaf. Its head is made of a series of five-petaled, five-stamened purple flowers.
	Hydrophyllum virginianum The Virginia Waterleaf is an herbaceous perennial plant native to Eastern North America. The plant spreads by rhizomes to form large colonies in wooded areas. Flowers are blue, white, or purple, appearing in mid to late spring.
	Hydroplane racing Hydroplane racing is a sport involving racing hydroplanes on lakes and rivers. It is a popular spectator sport in several countries, and one of the more commercialized sports.
	Hydroponics Hydroponics is agriculture production with mineral nutrient solutions instead of soil containing silt and clay. Terrestrial plants may be grown with their roots in the mineral nutrient solution only or in an inert medium, such as sand, gravel or rockwool.
	Hydrosphere Hydrosphere in physical geography, describes the collective mass of water found on, under, and over the surface of a planet.
	Hydrotherapy Hydrotherapy, formerly called hydropathy, is probably the oldest form of medical treatment. It involves the use of water for soothing pains and treating diseases. Its use has been recorded as early as ancient Ancient Egypt, Ancient Greece and Ancient Rome civilizations.
	Hydroxychloroquine Hydroxychloroquine is an antimalarial drug, sold under the trade name Plaquenil®, also used to reduce inflammation and in the treatment of arthritis and Lupus erythematosus.
	Hydroxyproline 4-Hydroxyproline, or hydroxyproline, is an uncommon amino acid, abbreviated as HYP, e.g., in Protein Data Bank. Its IUPAC name is 4-hydroxypyrrolidine-2-carboxylic acid. Hydroxyproline differs from proline by the presence of a hydroxyl group attached to the C atom. Other hydroxyprolines also exist in nature, notably 2,3-cis 3,4-trans-dihydroxyproline, which occurs in diatom cell walls, and is postulated to have a role in silica deposition.
	Hydroxyzine Hydroxyzine is a piperazine derivative that is used as an antihistamine, anti-emetic, and anxiolytic medication. It can also be used as an adjunct to pre- and post-operative medication and it also possesses a weak analgesic effect. Hydroxyzine is sold under brand names such as Atarax, Ucerax, Serecid and Vistaril.
	Hydrozoa Organisms that are in Class Hydrozoa come from the phylum Cnidaria. Most species of Hydrozoa are ocean and colonial and their Biological life cycle includes both the asexual polyp and the sexual Medusa stages. Medusas have a well-developed muscular velum that helps them move through water.
	Hyena Hyenas are moderately large terrestrial carnivores native to Africa and the Indian Subcontinent. They are members of the family Hyaenidae.
	Hygrometer There are several types of hygrometers that are commonly used, one is specifically known as a "psychrometer" and consists of two thermometers, one of which has its bulb constantly kept wet which measures the wet-bulb temperature. Evaporation from the bulb lowers the temperature so that this thermometer usually shows a lower temperature than that of the dry bulb thermometer.
	Hygrophoraceae The family Hygrophoraceae, also known as waxy caps or waxcaps, is a taxon of white-spore agarics. The common name "waxy cap" comes from the waxy feel and appearance of the lamellae and often of the entire fruiting body. The lamellar attachment ranges from adnate to subdecurrant, and the lamellae themselves are typically widely spaced.
	Hyla The genus Hyla is one of approximately 38 genera in the New World family of tree frogs. The word Hyla translates to "tree," and tree frogs are indeed arboreal. They have a very broad distribution; species can be found in Europe, Asia, Africa, and across the Americas.
	Hylas In Greek mythology, Hylas was the son of King Theiodamas of the Dryopians. When Heracles killed his father in battle, he spared Hylas, took him on as arms bearer, taught him the ways of a warrior, and in time the two fell in love. Heracles took Hylas with him on the Argo, making him one of the Argonauts.
	Hylobates The genus Hylobates is one of the four genera of gibbons. It was once considered the only genus, but recently its subgenera have been elevated to the genus level. Hylobates remains the most speciose and widespread of gibbon genera, ranging from southern China to western and central Java.
	Hylocereus Hylocereus is a genus of cactus, often referred to as nightblooming cactus. Several species have large edible fruits, which are known as pitaya or dragonfruits.
	Hymen The hymen is a fold of mucous membrane which surrounds or partially covers the external vaginal opening. It forms part of the vulva, or external genitalia, and is present in all females at birth. The most common formation of the hymen is crescentic or crescent-shaped, although several other formations are possible.
	Hymenium The hymenium is the tissue layer on the hymenophore of a fungal fruiting body where the cells develop into basidium or ascus, which produce spores. In some species all of the cells of the hymenium develop into basidia or asci, while in others some cells develop into sterile cells called basidioles or paraphyses.
	Hymenoptera Hymenoptera is one of the larger order s of insects, comprising the sawflies, wasps, bees, and ants. The name refers to the wings of the insects, which are membranous with the Insect_wing "married" to the Insect_wing by a series of hooks called hamuli.
	Hynerpeton Hynerpeton was a basal carnivorous tetrapod. Like many primitive tetrapods, it is sometimes referred to as an "amphibian", though it is not a true member of the class Amphibia. The Late Devonian saw the evolution of plants into trees and growing into vast forests pumping oxygen into the air, possibly giving Hynerpeton an edge because it evolved complex lungs to exploit it.
	Hyoscyamine Hyoscyamine is a chemical compound, a tropane alkaloid it is the levo-isomer to atropine. It is a secondary metabolite of some plants. Brand names for hyoscyamine include Symax, Anaspaz, Cystospaz, Levsin, Levbid, Donnamar, NuLev, and Neoquess.
	Hyperbola In mathematics, a hyperbola is a type of conic section defined as the intersection between a right circular conical surface and a plane which cuts through both halves of the cone. It may also be defined as the locus of points where the difference in the distance to two fixed points is constant.
	Hyperbolic geometry Hyperbolic geometry is a non-Euclidean geometry, meaning that the parallel postulate of Euclidean geometry is rejected. The parallel postulate in Euclidean geometry states that given a line l and a point P not on l, there is a unique line through P that does not intersect l.
	Hyperboloid In mathematics, a hyperboloid is a quadric, a type of surface in three dimensions, described by the equation  (hyperboloid of one sheet), or  (hyperboloid of two sheets) If, and only if, a = b, it is a hyperboloid of revolution. A hyperboloid of one sheet can be obtained by revolving a hyperbola around its transversal axis.
	Hypericum Hypericum is a genus of about 400 species of flowering plants in the family Clusiaceae, formerly often treated separately in their own family the Hypericaceae. The genus has a nearly world-wide distribution, missing only from tropical lowlands, deserts and arctic regions.
	Hypermarket In commerce, a hypermarket is a superstore which combines a supermarket and a department store. The result is a gigantic retail facility which carries an enormous range of products under one roof, including full lines of groceries and general merchandise. When they are planned, constructed, and executed correctly, a consumer can ideally satisfy all of his or her routine weekly shopping needs in one trip to the hypermarket.
	Hyperon In particle physics, a hyperon is any subatomic particle which is a baryon with non-zero strangeness, but with zero Flavour and zero bottomness.
	Hyperopia Hyperopia, also known as hypermetropia or colloquially as farsightedness, is a defect of visual system caused by an imperfection in the eye, causing inability to focus on near objects, and in extreme cases causing a sufferer to be unable to focus on objects at any distance.
	Hypertonic In biology, a hypertonic cell environment has a higher concentration of solutes than in cytoplasm. In a hypertonic environment osmosis causes water to flow out of the cell. If enough water is removed in this way, the cytoplasm will have such a small concentration of water that the cell has difficulty functioning.
	Hypertrophic cardiomyopathy Hypertrophic cardiomyopathy, or HCM, is a disease of the myocardium in which a portion of the myocardium is left ventricular hypertrophy without any obvious cause.1,10,22,29-31 Though perhaps most famous as a leading cause of sudden cardiac death in young athletes2 HCM's more important significance is as a cause of sudden unexpected cardiac death in any age group and as a cause of disabling cardiac symptoms.
	Hypertrophy Hypertrophy is the increase of the size of an organ. It should be distinguished from hyperplasia which occurs due to cell division; hypertrophy occurs due to an increase in cell size rather than division. It is most commonly seen in muscle that has been actively stimulated, the most well-known method being exercise.
	Hypervelocity Hypervelocity usually refers to a very high velocity, typically over 3,000 metre per secondApproximate values. In particular, it refers to velocities sufficiently high that the strength of materials is very small compared to inertial stresses. Thus, even metals behave like fluids under hypervelocity impact.
	Hypha A hypha is a long, branching filament found primarily in fungus, but also in fungus-like bacteria such as Actinomyces and Streptomyces. In fungi, the hyphal filaments form the feeding thallus, called the mycelium. Thallus, from the Greek thallos, means green shoot and is the actively growing vegetative form of a hypha.
	Hypnosis Hypnosis is a Psychology condition in which some people may be induced to show various differences in behaviour and thinking. Although some individuals experience an increase in suggestibility and subjective feelings of an 'altered state of consciousness', this is not true for everyone.
	Hypochlorite The hypochlorite ion is ChlorineOxygen-. A hypochlorite compound is a chemical compound containing this group, with chlorine in oxidation state +1. Hypochlorites are the salts of hypochlorous acid. Common examples include sodium hypochlorite and calcium hypochlorite.