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
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'
Webster Dictionary
1. h the eighthletter of the English alphabet, is classed among the consonants, and is formed with the mouthorgans in the sameposition as that of the succeeding vowel. It is used with certain consonants to form digraphs representing sounds which are not found in the alphabet, as sh, th, /, as in shall, thing, /ine (for zh see /274); also, to modify the sounds of some other letters, as when placed after c and p, with the former of which it represents a compoundsoundlike that of tsh, as in charm (written also tch as in catch), with the latter, the sound of f, as in phase, phantom. In some words, mostly derived or introduced from foreign languages, h following c and g indicates that those consonants have the hard sound before e, i, and y, as in chemistry, chiromancy, chyle, Ghent, Ghibelline, etc.; in some others, ch has the sound of sh, as in chicane. See Guide to Pronunciation, // 153, 179, 181-3, 237-8
Definitions of h 
