confidant /kon-fi-dantˈ/ or (fem) confidanteˈ noun

1. A person confided in or entrusted with secrets, esp in love affairs
2. A close friend

confidence /konˈfi-dəns/ noun

1. Firm trust or belief
2. Faith
3. Trust in secrecy
4. Self-assurance, self-belief
5. Assuredness, esp in the outcome of something
6. Admission to knowledge of secrets or private affairs
7. A confidential communication

conˈfidency noun

conˈfident adjective

1. Trusting firmly
2. Having full belief
3. (esp self-)assured
4. Bold

A confidential friend

confidential /-denˈshl/ adjective

1. Given in confidence
2. Admitted to a person's confidence
3. Private

confidentialˈity noun

confidenˈtially adverb

conˈfidently adverb

confīdˈer noun

confīdˈing adjective

Trustful

confīdˈingly adverb

confīdˈingness noun

confidence interval noun (statistics)

An interval so constructed as to have a prescribed probability of containing the true value of an unknown parameter

confidence trick noun

A swindler's trick, whereby (usu) a person is induced to hand over money to the swindler for something they will never receive (often shortened to con trick; see con¹)

confidence trickster noun

confident person noun (Scots law)

A confidential person, partner, agent, etc

in confidence

Secretly, as a secret

in someone's confidence

Trusted by the person in question with confidential matters