Number sign is a name for the symbol #, which is used for a variety of purposes, including (mainly in Canada and the United States) the designation of a number (for example, "#1" stands for "number one"). In recent years, it has been used for "hashtagging" on social media websites.The term number sign is most commonly used when the symbol is used before a number. In the United States, it is sometimes known as the pound sign, and has been traditionally used in the food industry as an abbreviation for pounds avoirdupois. Outside of North America the symbol is called hash and the corresponding telephone key is called the "hash key", and the term "pound sign" usually describes the British currency symbol "£". The symbol is defined in Unicode as U+0023 # number sign (HTML: # as in ASCII).The symbol may be confused with the musical symbol called sharp (♯). In both symbols, there are two pairs of parallel lines. The main difference is that the number sign has two horizontal strokes while the sharp sign has two slanted parallel lines which must rise from left to right, in order to avoid being obscured by the horizontal musical staff lines.