- (with two objects) To inform (someone) (of something).
- I sent an e-mail to let John know what we found.
- Let me know when you are arriving .
- "I'm not sure which flight I'll be taking." / "Well, as soon as you find out, let me know."
- He let her know about his plans.
- If anyone has seen him, let us know of his whereabouts.
- The second object may be omitted when it is understood in context.