Key Difference: Secret defines something that is kept hidden so that it remains unseen or unknown to others. Confidential refers to something that is intended to be kept as a secret. In context to information, the term secret is associated with more sensitive and important information than confidential information.

Secrets are intended to be kept forever and thus, should remain unrevealed. A secret can be a tangible or a non tangible entity. For example, a recipe book of a special strawberry chocolate that is kept at a secret place is a tangible secret item. However, a secret recipe that is not written but is only shared verbally is a non tangible secret.

Many times, secret and confidential are used interchangeably. Casually, secret is preferred over confidential in day to day life, like: secret between two friends, a secret location to keep the house keys, etc. On the other hand, confidential is generally related to official usage like confidential files, confidential papers, etc. The major difference arises when they specify the category of information. Information pertaining to national security is often categorized into three categories comprising of top secret, secret and confidential. In this aspect, they differ immensely.

According to the U.S. classification of information system:-

 "Secret" shall be applied to information, the unauthorized disclosure of which reasonably could be expected to cause serious damage to the national security.

"Confidential" shall be applied to information, the unauthorized disclosure of which reasonably could be expected to cause damage to the national security.

The difference can easily be observed by the use of word serious in secret. Therefore, it pertains to the information that needs to be more carefully handled than the confidential information, referring to important and significant information.

Secret is used as a noun and adjective.

Example- She shares many secrets with her friends.

She kept a secret for a long time.

We found a secret room in the old house.

However, confidential is always used as an adjective.

Example- All confidential files must be kept in lockers.

Therefore, secret and confidential are synonymous, according to their definitions. However, secret is generally used in a casual way to denote an entity that is protected from being disclosed. Confidential is generally opted to formally denote a secret. In terms of information, a secret refers to more important and serious information than the confidential information. Thus, it depends upon the context, and based on it, the appropriate word can be used.

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