Most of the time when radio is used for communication it is critical that each side decodes the message properly. Some examples of important situations would be Air traffic control towers, police radios, and army communications. For example, in the army you never say repeat on the radio. You always say "say again" if you want the person to repeat what they just said. If your talking to the artillery or infantry on the radio and say "repeat" the soldiers will send an artillery shell down range in the same place it was fired before. This could be problematic if soldiers are surveying the area just bombed.
Below is a radio communications guide so you can better understand how to communicate on the radio