A responder is someone who answers or reacts to something. When your teacher asks a question in class, the student who raises their hand and gives an answer is a responder. When you text your friend and they write back, they're responding to your message.

The word takes on special importance in emergencies. First responders are the professionals who rush to help when something goes wrong: firefighters, police officers, paramedics, and emergency medical technicians. When someone calls 911, first responders are the ones who arrive at the scene to provide immediate help. They're called first responders because they're trained to be the first people on site during a crisis, such as a car accident, a fire, or a medical emergency.

In everyday situations, a quick responder answers messages or questions without unnecessary delay. A thoughtful responder takes time to give helpful, considered answers rather than rushing through them.

The opposite of a responder would be someone who ignores questions, stays silent when input is needed, or fails to react when action is required. In group projects, reliable responders are the teammates who actually reply when you ask them something, while poor responders leave you wondering whether they even saw your message.