From WordNet (r) 3.0 (2006):
H
n 1: 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 [syn: hydrogen, H, atomic number 1]
2: 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 [syn: henry, H]
3: the constant of proportionality relating the energy of a
photon to its frequency; approximately 6.626 x 10^-34 joule-
second [syn: Planck's constant, h]
4: the 8th letter of the Roman alphabet [syn: H, h]
5: (thermodynamics) a thermodynamic quantity equal to the
internal energy of a system plus the product of its volume
and pressure; "enthalpy is the amount of energy in a system
capable of doing mechanical work" [syn: heat content,
total heat, enthalpy, H]