1st_ Fifth vowel in Spanish. 2º_ It is used as the conjunction 'o' in cases where the next word begins with the letter /o/. In chemistry, 'u' is the symbol for the unit of atomic mass. 'U' is the chemical symbol for uranium. 5º_ 'U' is a municipality in the state of Ponapé in the Federated States of Micronesia. See u . ("short for 'use'].
