planck's constant: the constant of proportionality relating the energy of a photon to its frequency; approximately 6.626 x 10^-34 joule-second
entity: that which is perceived or known or inferred to have its own distinct existence (living or nonliving)
metasequoia: large fast-growing Chinese monoecious tree having flat bright-green deciduous leaves and small globular cones; commonly cultivated in United States as an ornamental; known as a fossil before being discovered in China