The U symbol means "union". A union of two sets means that the distinct elements of each set are combined together. For example, the union of {1,2,3} and {4,5,6} is {1,2,3} U {4,5,6} = {1,2,3,4,5,6}....
In mathematics, more specifically quadratics, it refers to "OR." As opposed to "AND", which is represented by an upside down "U", it is to be solved by drawing a graph of two (or more) lines and...
The term "sailing" is also used for submarines - the definition of "sailing" has several meanings besides the one most people think about, which is wind billowing through canvas of a sailing vessel....