signal

A gesture, sound, or action that is used to convey information or instructions, or to indicate a particular state or condition. It can also refer to an electrical impulse or radio wave that transmits information or sound, or a notable event or piece of information that indicates something significant.

• The traffic light turning green was a signal for the cars to go. — This example shows a physical signal conveying instructions.
• His sudden resignation sent a strong signal that he was unhappy with the new management. — This example demonstrates 'signal' as a non-physical indicator of a situation or feeling.
• The radio receiver picked up a faint signal from deep space. — This example refers to an electronic signal.

To make a gesture, sound, or other action to convey information or a message. It can also mean to indicate, show, or communicate something important or a particular state.

• She signaled her approval with a nod. — This example shows using a gesture to convey a message.
• The low attendance numbers signaled a lack of interest in the event. — This example shows how data can indicate a condition.
• The lifeguard signaled to the swimmers that it was safe to enter the water. — This example shows communicating instructions.

Used to describe something that is particularly important, notable, or outstanding, often serving as a sign of something significant to come or a turning point.

• The company's new breakthrough was a signal achievement in biotechnology. — This example describes an outstanding achievement.
• Winning the championship was a signal moment in the team's history. — This example refers to a notable and important event.