noun (n)

• the boundary of a specific area(noun.location)

  Synonym:
  demarcation line, limit
  

  source: wordnet30
• a conceptual separation or distinction(noun.cognition)

  Synonym:
  contrast, dividing line, line
  

  source: wordnet30
• The act of marking, or of ascertaining and setting a limit; separation; distinction.(noun)

  source: webster1913