U is a letter in the american alphabet, which has the ability to become invisible in some words. In American, the letter appears at least once in every word. Perhaps the most well known example is the word "Colour", which, when rendered in American, is written "Color". the u, while still present, and vital to the spelling, is entirely invisible. Another key example is the word commonly spelled "You", which in truth, is spelled (with all invisible U's shown):