What is meant by “check” in a radiogram header?

In a formal radiogram, the "check" is an accounting tool used to ensure the message was transmitted and received completely and accurately. It is simply the count of the number of words, or word equivalents, strictly within the text portion of the message. When receiving a message, operators count the words in the text body and compare it to the "check" number provided in the header. If the numbers match, the message was likely received without missing any words. Distractors suggesting it refers to the originating station or a list of relays misinterpret the NTS definition of the word "check."