What keyword indicates that a radio message has been received and understood?

The keyword that indicates a radio message has been received and understood is "Roger." In radio communication, "Roger" is commonly used to confirm that a message has been received and understood correctly. This term is rooted in aviation and military communications, signifying clear acknowledgment. It helps in ensuring effective communication, especially in situations where clarity is critical, as it minimizes the chance of any misunderstanding.

While "Acknowledged" and "Received" can also indicate receipt of a message, they do not inherently imply understanding. "Understood" is abstract and may not be a standard term used in radio protocols to convey acknowledgment. Using "Roger" is the most recognized and conventional method in communications to express both receipt and comprehension of the transmitted information.