Definition of "common knowledge" []

• What "everybody knows", often with reference to a specific community; something which cannot reasonably be contested. (noun)
• A special kind of knowledge for a group of agents, such that when all the agents in a group G know p, they all know that they know p, they all know that they all know that they know p, and so on ad infinitum. (noun)

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• "Langsdorff had already sent word to the Harbourmaster that the Graf Spee would sail at or shortly after 1815, and this news soon became common knowledge among the crowd."
• "IT was common knowledge that Smugg was engaged to be married."
• "It was common knowledge among the people on the campus that wherever Zhao Hongbo was, there you would find Shen Xue too."