#

The pound symbol (also known as the "hash" symbol) is most commonly used to represent numbers, as in, "I'll answer #3." In some versions of Unix, it is the system prompt. It has a variety of uses online, either as part of a cryptic password, or in creative renditions of ASCII art, in smileys, or it is added to a word or phrase that lets Twitter users search for tweets similarly tagged, for example: #wordoftheday. It also means "net."