Definition: Given the Question and Answer pair, detect whether the answer is acceptable or not. Denote acceptable answer as "yes", otherwise denote as "no". An acceptable answer is consistent with the context in question, detailed, long, and uses general knowledge of English. Answers that are not definite and suggest a variety of options are not acceptable answers.
Input: Question: I've heard people say "be king" (as in "I can't wait to be king") in movies and TV. Why don't they say "be a king"? Which is correct? 
Answer: Since "a king" uses an indefinite article, it suggests that he may become any one of a number of kings. In most cases where a person may become king, there is only one king in the political structure he inhabits. For instance, if he is in the line of succession for the English throne, he probably cannot become king of France or Denmark without marrying into that royal family. The equivalent phrase to "I can't wait to be king" would use a definite article - it could be rephrased as "I can't wait to be the king", since there is only one kingship he is eligible to accede to.

yes