secret

Confidential, private, privileged, or proprietary information kept away from the attention, knowledge, or observation of others, and shared only with authorized, concerned, or trusted parties. Unauthorized disclosure of a secret may constitute a breach of trust.

It is inconceivable that anyone will divulge a truly effective get-rich scheme for the price of a book . . . There is ample opportunity to use wealth in this world, and neither I nor my friends, nor anyone else I have ever met, has so much of it that they are interested in putting themselves at a disadvantage by sharing their secrets.

• One Secret to Life