1. (noun)hydrogen, H, atomic number 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
2. (noun)henry, H 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
3. (noun)Planck's constant, h the constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second
5. (noun)heat content, total heat, enthalpy, H (thermodynamics) a thermodynamic quantityequal to the internal energy of a systemplus the product of its volume and pressure "enthalpy is the amount of energy in a system capable of doing mechanical work"
Definition of 'H' 
