No.

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numero sign

Wikipedia

• №, Nº, Nº.
• No, no., no

Borrowing of the Latin scribal abbreviation No. from (in) numerō (“in number, to the number of”). Cognate with French n^o.

• Audio (US); “number”:

  (file)

No. (not comparable)

1. (archaic) Abbreviation of in number or to the number of.
   • 1661, Robert Lovell, A Compleat History of Animals and Minerals, page 129:

     They goe two months, & then bring forth a blind off-spring like bitches, n^o. eight or nine.

   • 1693, Steven Blankaart, A Physical Dictionary, 2nd edition, page 146:

     Take of Jujubes N^o vi. that is, Six in number.

   • 1994, Dorland's Medical Dictionary, 28th edition, page 1141:

     No., abbreviation of L. numero, ‘to the number of’.

No. (plural Nos.)

1. Abbreviation of number.
   • 1753, A Supplement to Mr Chambers's Cyclopaedia, s.v. "Otis":

     See Tab. of Birds, N^o 28.

   • 1840 February 4, Charles Dickens, letter:

     I am curious to see how the idea of the first No. of my projected work, strikes you.

   • 1974, Michael Gilbert, Flash Point, page 14:

     It's No. 276 Coalporter Street.

   The king made a gift of No. 10 to his old Eton roommate.

This is the customary abbreviation for number used in case citations.

• #
• №

• “No., adv.³ and n.².”, in OED Online ⁠, Oxford: Oxford University Press, 2003.
• The Bluebook, 19th ed. (2010), "Case Names and Institutional Authors in Citations", Table T6, pp. 430-431.

• -on, ON, ON., on, on-