The numero sign or numero symbol, № (also represented as Nº, No, No. or no., plural Nos. or nos.) is a typographic abbreviation of the word number(s) indicating ordinal numeration, especially in names and titles. For example, with the numero sign, the written long-form of the address "Number 22 Acacia Avenue" is shortened to "№ 22 Acacia Avenue", yet both forms are spoken long.
Typographically, the numero sign combines the upper-case Latin letter N with a usually superscript lower-case letter o, sometimes underlined, resembling the masculine ordinal indicator. In Unicode, the character is U+2116 № numero sign (HTML:
The Oxford English Dictionary derives the numero sign from Latin numero, the ablative form of numerus ("number", with the ablative denotations of: "to the number, by the number, with the number"). In Romance languages, the numero sign is understood as an abbreviation of the word for "number", e.g. Italian numero, French numéro, and Spanish, Portuguese and Galician número.
The numero sign, despite its widespread usage internationally, is not a standard alphabetic symbol in virtually any European languages.
In English, the abbreviation "No." of "numero" is often used in place of the word "number". In US English the number sign # is used as a prefix to designate Numbers, and at the end of a number to designate pounds. 
The numero symbol is not in common use in France and does not appear on a standard AZERTY keyboard. Instead, the French Imprimerie nationale recommends the use of the form "no" (an "n" followed by a superscript lowercase "o"). The plural form "nos" can also be used. In practice, the "o" is often replaced by the degree symbol (°), which is visually similar to the superscript "o" and is easily accessible on an AZERTY keyboard. Use of the similar ordinal indicator (º), used in some other European languages, is not advised in French.
The numero sign is not a typographic symbol character, but the word número (number) abbreviated per the Spanish typographic convention of superior letters — letras voladas (flying letters) and voladitas (little flying letters) — wherein the final letter(s) of the abbreviated word are written as underlined lower-case superscripts: no and No (singular), nos and Nos (plural), which is in the same fashion as other flying letters like Fco for Francisco; Ma for María; fdo for firmado (signed). The substitutive form 'No.' is not used because that might be confused for the Spanish word no. Acceptable alternatives in case no other typographic option is available are: Nro., nro. or núm. (the dots are part of the abbreviation). Flying letters also indicates a masculine ordinal number, 1o primero (first), 2o segundo (second), 3o tercero (third), and so on, or a feminine ordinal number: "primera" 1a, "segunda 2a, tercera 3a, etc.
Portuguese orthographic rules don't allow the usage of №, because, as it is an abbreviation, it is necessary to place a period before the superscript O: 'n.o' and not 'no' (plural: n.os). It is, however, a common mistake, and even newspapers and media often write 'no' or even 'no.'. Another reason why № is not acceptable, is that número (number) is not spelled with capital N, and so, its abbreviated form follows the same rule. As in Spanish, 'no.' is an unacceptable, ambiguous usage that might be confused for no (a contraction of em (in) and o (the), the masculine singular definite article). The ordinal indicators are also used to indicate the gender of a title: Prof.a = professor'a' (female teacher/professor), in contrast to Prof. In fact, there is no limit for which words may be abbreviated this way. For example: Ex.mo for Excelentíssimo (an honorific), L.da for Limitada (Ltd.), Sr.a for Senhora (Ms.), etc. Traditionally, it should be underlined, however, due to the fact that many fonts don't display the symbol in such way, this usage is slowly disappearing.
Typographic conventions for abbreviations are like those of Spanish, but superscripts are rarely used, except in the numero sign. The sign is usually replaced with the abbreviations "n." or "no", the latter comprising the ordinal symbol. Similar superscript is also used for primo 1o and prima 1a, secondo 2o and seconda 2a, terzo 3o and terza 3a, etc.
Indonesian and Malaysian
Typing the symbol
On typewriters and computers that do not support this symbol, it is acceptable and commonplace to replace it with the trigraph "No." (letter "N", letter "o", and a period (full stop)).
On typewriters and computers that support the degree symbol or (preferably) masculine ordinal indicator, a digraph starting with "N", such as "N°" or "Nº", may suffice as a substitute for the numero sign, but only if it is to be presented exclusively within visual media, in a typeface and sizing that results in a passable approximation of the numero sign. Such digraphs are inappropriate for representing the numero sign in computer data, in general.
On Russian computer keyboard layout, the № is available and often located on the 3 key.
In Mac OS X, the character can be typed using "U.S. Extended" and "Irish Extended" keyboard layouts by typing ⇧ Shift+⌥ Option+;.
In HTML, the numero sign (if it cannot be entered directly) may be represented by
U+2116 NUMERO SIGN is provided both for Cyrillic use, where it looks like [semi-cursive "N" followed by raised, underlined small "o"], and for compatibility with Asian standards, where it looks like [angular "N" followed by raised, underlined small "o", followed by a period]. …Instead of using a special symbol, French practice is to use an "N" or an "n", according to context, followed by a superscript small letter "o" (No or no; plural Nos or nos). Legacy data encoded in ISO/IEC 8859-1 (Latin-1) or other 8-bit character sets may also have represented the numero sign by a sequence of "N" followed by the degree sign (U+00B0 degree sign). Implementations working with legacy data should be aware of such alternative representations for the numero sign when converting data.
- "no. or No.". The American Heritage® Dictionary of the English Language. Houghton Mifflin Company. 2009. Retrieved May 13, 2013.
- "nos. or Nos.". The American Heritage® Dictionary of the English Language. Houghton Mifflin Company. 2009. Retrieved May 13, 2013.
- Machinery's Handbook 21st Ed
- Lexique des règles typographiques en usage à l’Imprimerie nationale (in French). Imprimerie nationale. 2002. ISBN 978-2-7433-0482-9.
- Lacroux, Jean-Pierre. "De navire à numéro". Orthoypographie (in French)..
- Antonio Fernandez Fernandez. Diccionario de dudas (Doubts dictionary) - Vol. 2. P. 108.
- "La corrispondenza italiana: abbreviazioni". Retrieved 2010-05-17.
- The Unicode Standard 5.0 — 15.2 Letterlike Symbols. The Unicode Consortium. 2007. Retrieved 2009-09-11.