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
