Why there is no article before words like queen and king? [duplicate]

Solution 1:

I believe this might be clarified with capitalization (though such capitalization is often optional). As tom noted in his answer, this tends to apply when there is only one such position in context.

You will be King one day.

With the capitalization, you can then imply the following.

You will be King Robert one day.

It's not so much that "king" is the noun, but the title. We can apply this further.

I want to be President when I grow up.

One of the examples you provided in response to tom's answer makes sense, too, and you might see it in Dan Brown's book, "Angels and Demons". (I'm constructing a sample sentence with that context.)

He aspired to be Pope, though he was ineligible as a candidate.

Where the noun can serve as a title, you may find it used without the article.

Regardless of what atrocities he committed on the way, he is Lord High Emperor; we have no recourse.

Solution 2:

I think this is to do with there only being one king or one queen.

'You will be prime minister' is another example where there is one prime minister - but 'you will be minister' where there are many ministers is not correct.

'you will be director general' - works too for an organization where there is one director general.

Now you can also say 'you will be the king', but 'you will be king' sounds better.