A "nod" is a quick movement of the head, typically downward and upward, often used to indicate agreement or acknowledgment. It is a common non-verbal gesture in many cultures, conveying a simple "yes" or understanding without the need for words. In social interactions, a nod can also serve as a greeting or a way to show attentiveness. For example, during a conversation, a person might nod to signal that they are listening to the speaker, enhancing communication and connection between individuals.