h h /ˈeɪtʃ/

noun

1. The constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second  ( h , Planck's constant )
   the constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second
   

 H

1. (thermodynamics) a thermodynamic quantity equal to the internal energy of a system plus the product of its volume and pressure  ( H , heat content , total heat , enthalpy )
   (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
   enthalpy is the amount of energy in a system capable of doing mechanical work
   
2. The 8th letter of the Roman alphabet  ( H )
   the 8th letter of the Roman alphabet
   
3. 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  ( H , henry )
   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
   
4. 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  ( atomic number 1 , H , hydrogen )
   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
     Hydrogen is the lightest and most abundant element in the universe.
   Hydrogen is the lightest and most abundant element in the universe.