U字開頭的單詞或詞組
up to nowunableup-to-dateulcerative colitisUSAunfortunatelyunexpectedlyU-turnustinultimatelyusingunitaryunrecognized commandunderlyinguncertaintyUFOunityup to dateuntitledU.K.ubiquitousuncertainunlessuseruptakeundermineunpackUnited Nationsunder wayurnupside downunderstandingunblockupsideUNOumpunauthorizedUHFunfortunateunveilunrestrainedunfolding