The numero sign or numero symbol, № (also represented as Nº, No̱, No. or no.), is a typographic abbreviation of the word number(s) indicating ordinal numeration, especially in names and titles. For example, using the numero sign, the written long-form of the address "Number 29 Acacia Road" is shortened to "№ 29 Acacia Rd", yet both forms are spoken long.
Sign showing the rarer Nͦ form in Italy
The symbol # is known variously in English-speaking regions as the number sign, hash, or pound sign. The symbol has historically been used for a wide range of purposes including the designation of an ordinal number and as a ligatured abbreviation for pounds avoirdupois – having been derived from the now-rare ℔.
The abbreviation written by Isaac Newton, showing the evolution from "℔" toward "#"
Detail of a telephone keypad displaying the Viewdata square