/ Thesaurus / P Synonyms of planck's constant Find synonyms for: Noun1. Planck's constant, h, factor of proportionality, constant of proportionalityusage: the constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-secondWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: bibliophile Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language