usefulness

n. 有用, 有效性

urgent, urgently, uric, urinal, urinary, urinate, urine, urn, us, USA, usable, USAF, usage, use, use up, used, used to, used to do, useful, usefully, useless, uselessly, uselessness, user, user-friendly, usher, usherette, USN, USS, USSR, usual, usually, usurer, usurp, usurpation, usurper, usury, Utah, utensil, uterine,