Hn. (thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure ; Hn. the 8th letter of the Roman alphabet ; hn. the constant of proportionality relating the energy of a photon to its frequency ; approximately 6.626 x 10^-34 joule-second ; Hn. a unit of inductance in which an induced electromotive force of one volt is produced when the current is varied at the rate of one ampere per second ; Hn. a nonmetallic univalent element that is normally a colorless and odorless highly flammable diatomic gas ; the simplest and lightest and most abundant element in the universe ; H-bombn. a nuclear weapon that releases atomic energy by union of light (hydrogen) nuclei at high temperatures to form helium ; H-shapedadj. shaped in the form of the letter H ; H. G. Wellsn. prolific English writer best known for his science-fiction novels ; he also wrote on contemporary social problems and wrote popular accounts of history and science (1866-1946) ; H. H. Munron. British writer of short stories (1870-1916) ; H. J. Eysenckn. a British psychologist (born in Germany) noted for his theories of intelligence and personality and for his strong criticism of Freudian psychoanalysis ; H. L. Menckenn. United States journalist and literary critic (1880-1956) ; H. pylorin. the type species of genus Heliobacter ; produces urease and is associated with several gastroduodenal diseases (including gastritis and gastric ulcers and duodenal ulcers and other peptic ulcers) ; H.I.n. a group of volcanic and coral islands in the central Pacific ; H.M.S. Bountyn. a ship of the British navy ; in 1789 part of the crew mutinied against their commander William Bligh and set him afloat in an open boat ; H.P.n. a unit of power equal to 746 watts ;
