U

U, 21st letter of the English alphabet, corresponding to the Semitic letter waw, meaning “hook,” represented by a tenthook symbol and probably derived from an ancient Egyptian symbol for a pole support. The Greeks altered it to Y, and as the 20th letter of the Roman alphabet it became V, representing both U and V sounds. The use of U for the U sound dates from the Middle Ages. U is also the chemical symbol for the element uranium.