Yu 成语
yucky
" terrible; distasteful; very unpleasant."
yuk
awful, gross, ugly "When Jenny cooks beef liver, the kids say, ""Yuk!"""
yum
it tastes good, I like it Yum! This soup is good!
yummy
delicious.
yuppie
young, upwardly-mobile, professional person The yuppies are buying BMW's, but can they afford them?
ayuh
(Maine) yes. This is always said quietly on an intake of breath, no matter how momentous the question, and with a rising inflection denoting resigned optimism:"Did you just see that out-of-control Mac truck bearing a load of plutonium crash through the wall of your mobile home and explode in flames?'' "Ayuh"
yummy pants
an attractive female; "Check out the yummy pants at the bar"
yum-yum|yum
interj.,
informal 
Used usually by or to children, to express great delight, especially in the taste of food.
"Yum-Yum! That pie is good!"