Nod means to move your head down and then back up as a way of saying “yes,” showing agreement, or acknowledging someone. When your teacher asks if you understand the homework and you nod, you're answering without speaking. When someone tells you a story and you nod along, you're showing that you're listening and following what they're saying.

People nod for many reasons beyond just saying yes. You might nod to greet someone you pass in the hallway. A conductor might nod to signal the orchestra to begin playing. A friend might nod toward the door to suggest leaving without saying a word out loud.

The word also describes a quick, small sleep, usually unintentional. If you stayed up too late reading and start to nod off during class, your head begins to droop forward as you drift toward sleep. Someone who's exhausted might sit in a chair and nod off for a few minutes.

When something gets a nod of approval, it means someone has agreed to it or given permission, like when your principal gives a plan the nod to move forward. A knowing nod between friends suggests they both understand something without needing to say it out loud.