This is an article on the symbol #. The official name of the symbol is contested; it is most commonly known as a number sign, hash, hash sign, pound, or pound sign. Other names include octothorpe and hashtag. The symbol is used for a variety of purposes, including the designation of a number (for example, "#1" stands for "number one"), an abbreviation for pounds avoirdupois in the food industry, a searchable metadata tag on social media platforms, and a button on telephone keypads. The symbol is defined in Unicode as U+0023#NUMBER SIGN (HTML # ·as in ASCII).