Impossib/ility

• Impossibility

  • The state of being impossible: something that cannot happen, be done or be true.
  • The word covers several strengths of "cannot." A logical impossibility contradicts itself, like a square circle. A physical impossibility breaks a law of nature, like a perpetual motion machine. A practical impossibility is only out of reach with the means at hand.
  • In mathematics and computer science, an impossibility result proves that no method can achieve some goal, as the halting problem does for deciding whether any program finishes.