signal
Definitions
A gesture, sound, or action used to convey information, instructions, or a warning.
An electrical impulse or radio wave transmitted or received to convey data or images.
A noticeable event or fact that indicates the state or existence of something.
Examples
The lighthouse sent a bright signal across the dark ocean.
She gave me a subtle signal to let me know it was time to leave.
The poor cell phone signal made it difficult to complete the call.