/ Dictionary / Index Y Young's modulus: Meaning and Definition of Find definitions for: Young's' mod'ulus Pronunciation: [key] — Physics. Physics. a coefficient of elasticity of a substance, expressing the ratio between a stress that acts to change the length of a body and the fractional change in length caused by this force. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. Young Pretender youngster Related Content Daily Word Quiz: coincidence Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language