u or U 
/ˈju:/ noun
plural u's or U's /ˈju:z/ /ˈju:/ noun 1 : the 21st letter of the English alphabet [count] ▪ There are three u's in “unusual.” [noncount] ▪ a word that starts with u 2 [count] Brit : a grade given to a student whose work is judged as not satisfactory
