noun (n)

• a message expressing an opinion based on incomplete evidence(noun.communication)

  Synonym:
  conjecture, guess, hypothesis, speculation, surmisal, surmise
  

  source: wordnet30
• a hypothesis that is taken for granted(noun.cognition)

  Synonym:
  assumption, supposal
  

  source: wordnet30
• the cognitive process of supposing(noun.cognition)

  Synonym:
  supposal
  

  source: wordnet30
• The act of supposing, laying down, imagining, or considering as true or existing, what is known not to be true, or what is not proved.(noun)

  source: webster1913