secret
Definition
Something kept hidden or not known to others; also, something intended to be concealed.
हिन्दी कुछ ऐसा जो छिपाया गया हो या दूसरों को न ज्ञात हो; साथ ही, कुछ ऐसा जिसे छिपाया जाना है।
Example
"He shared a secret with his best friend after swearing him to silence."