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

  1. (cartography) Used to denote a village.
  2. (chess notation) Checkmate.
  3. (computing) The hash character.
  4. (Internet) A hashtag, which is a metadata tag for use in microblogging and social network services, used to label and search content.
  5. (Usenet) Used to pad the left side of a quotation from a manual or official source.
  6. (mathematics, computer science) Concatenation.
  7. (set theory) The cardinality of a set.
    #{ 5, 3, 7, 11 } = 4
  8. (phonology) Used to indicate a word boundary.
  9. (syntax) Used to indicate that a sentence is grammatical but semantically strange.
  10. Alternative form of

Usage notesEdit

In English it is called the hash, number sign, pound sign (American), or octothorpe (uncommon).


Coordinate termsEdit

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

Derived termsEdit



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