Unsupported titles/Number sign

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# (English symbol name number sign or hash or pound sign or octothorpe)

  1. (set theory) The cardinality of a set.
    #{ 5, 3, 7, 11 } = 4
  2. (computing) The hash character.
  3. (Internet) A hashtag, which is a metadata tag for use in microblogging and social network services, used to label and search content.
  4. (Usenet) Used to pad the left side of a quotation from a manual or official source.
  5. (mathematics, computer science) concatenation
  6. (Internet) The anchor in a page.
    1. Used in URLs, links to the anchored portion of the page.
      http://www.example.com/index.html#chapter14 goes to the "chapter14" anchor in the index.html page.
    2. The ID selector in CSS, which intends to format an element that appears only once in a page.
      div#currentchaptertitle {font-weight: bold}
  7. (syntax) Used to indicate that a sentence is grammatical but semantically strange.
  8. (phonology) Used to indicate a word boundary.
  9. Alternative form of
  10. (chess notation) checkmate
  11. (cartography) Used to denote a village.
  12. (programming) The length operator in Lua.


Derived termsEdit

Coordinate termsEdit

  • (to pad a quotation on Usenet): > (for a quotation not necessarily from a manual or official source)

Usage notesEdit


  • (chess): ++



The symbol # derives from the abbreviation lb for Latin libra (pound), via the medieval convention of indicating abbreviations with a bar, .


# (plural # or #s)

  1. (food packaging, US) Pound (unit of weight)
    3# — "three pounds"
  2. (followed by a numeral: used attributively) Number
    #3 — "number three"
  3. (linguistics) denotes a word or morpheme boundary

Related termsEdit


See alsoEdit