English Words Starting With H

• hydrocracking

  nounC2
  /ˈhaɪ.drəʊˌkræk.ɪŋ/An industrial chemical process used in oil refining where heavy hydrocarbon molecules are broken down (cracked) into lighter, more valuable ones (like gasoline) using hydrogen under high pressure and temperature.
• hydrocyanic acid

  nounC2
  /ˌhaɪ.drəʊ.saɪˈæn.ɪk ˈæs.ɪd/A colourless, volatile, extremely poisonous chemical compound with the formula HCN. It is a solution of hydrogen cyanide in water.
• hydrodesulfurization

  nounC2 / Technical
  /ˌhaɪ.drəʊ.diːˌsʌl.fjə.raɪˈzeɪ.ʃən/A chemical process that removes sulfur from petroleum or natural gas by reacting it with hydrogen.
• hydrodynamicist

  nounC2
  /ˌhaɪ.drəʊ.daɪˈnæm.ɪ.sɪst/A scientist or engineer who specializes in the study of fluids in motion, particularly liquids.
• hydrodynamics

  nounLow
  /ˌhaɪ.drəʊ.daɪˈnæm.ɪks/The branch of physics and engineering that studies the motion of fluids (liquids and gases) and the forces acting on solid bodies immersed in them.
• hydroelastic suspension

  nounVery Low / Niche Technical
  /ˌhaɪ.drəʊ.ɪˌlæs.tɪk səˈspen.ʃən/A mechanical system, typically in a vehicle, that uses the elasticity of contained fluid under pressure to absorb shocks and vibrations, often combined with gas or air.
• hydroflight

  nounVery Low
  /ˈhaɪ.drəʊ.flaɪt/A recreational or competitive activity where a person, wearing a jet-powered water propulsion device (jetpack or boots), is propelled into the air above a body of water.
• hydrofluoric acid

  nounVery Low
  /ˌhaɪ.drəʊ.flʊəˈrɪ.ɪk ˈæs.ɪd/A colourless, highly corrosive, and poisonous aqueous solution of hydrogen fluoride, used especially in etching glass and in industrial processes.
• hydrofluorocarbon

  nounC1
  /ˌhaɪ.drəʊˌflɔː.rəʊˈkɑː.bən/A compound containing only hydrogen, fluorine, and carbon atoms, used primarily as a refrigerant, propellant, or solvent.
• hydrofoil

  nounC1
  /ˈhaɪ.drə.fɔɪl/A boat equipped with wing-like structures (foils) mounted on struts underneath the hull that lift the boat out of the water at speed, reducing drag.
• hydroforming

  nounC1
  /ˈhaɪdrəʊˌfɔːmɪŋ/A metal forming process that uses high-pressure fluid to shape a workpiece.
• hydroformylation

  nounVery Low
  /ˌhaɪdrə(ʊ)fɔːmɪˈleɪʃ(ə)n/A chemical reaction where an alkene is converted into an aldehyde using carbon monoxide and hydrogen (syn-gas).
• hydrofracking

  nounC1
  /ˈhaɪ.drəʊˌfræk.ɪŋ/A method of extracting oil or natural gas from underground rock formations by injecting a high-pressure mixture of water, sand, and chemicals to fracture the rock and release the hydrocarbons.
• hydrofracturing

  nounLow
  /ˌhaɪdrəʊˈfræktʃərɪŋ/A method of extracting oil or gas by injecting high-pressure fluid into rock formations to create fractures.
• hydrogel

  nounC1/C2
  /ˈhaɪ.drəʊ.dʒel/A jelly-like substance composed mainly of water held in a porous polymeric network.
• hydrogen

  nounB2
  /ˈhaɪ.drə.dʒən/A chemical element, atomic number 1, symbol H, the lightest and most abundant element in the universe.
• hydrogen bomb

  nounC1
  /ˈhaɪdrədʒən bɒm/A nuclear weapon that derives its explosive energy from nuclear fusion of hydrogen isotopes, much more powerful than a fission-based atomic bomb.
• hydrogen bond

  nounC1
  /ˈhaɪdrədʒ(ə)n bɒnd/A relatively weak electrostatic attraction between a hydrogen atom (covalently bonded to a strongly electronegative atom like oxygen or nitrogen) and another electronegative atom with a lone pair of electrons.
• hydrogen bromide

  nounRare/Very Low Frequency
  /ˈhaɪdrədʒən ˈbrəʊmaɪd/A chemical compound with the formula HBr, formed from hydrogen and bromine; a colorless, corrosive, toxic gas or a solution of that gas in water (hydrobromic acid).
• hydrogen carbonate

  nounlow
  /ˈhaɪ.drə.dʒən ˈkɑː.bə.neɪt/The HCO₃⁻ ion or a salt containing this ion, commonly known as bicarbonate.

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