"king of" or "the king of"

Which is correct?

I am king of the world.

I am the king of the world.

Additionally, which would be the better choice, if I wanted to use the expression "king" to signify dominance in a metaphorical way or in slang.

I am king of the backstreet.

I am the king of the backstreet.

And is there a difference, if we are not king of a place but of a group of people?

I am king of (the) thieves.

I am the king of (the) thieves.

Is there a general grammatical rule for that?

Solution 1:

I can't find an authority on this, so this answer is based on my intuition and anecdotal evidence. That said, I think that technically you should include "the", though in this case you can get away without it.

The general rule is that if you use a noun in the singular and it is not a proper noun, it requires an article (or another adjective indicating "one", like the word "one"). So:

That man is the king. (article required)

But

That man is King Charles. (no article)

"King of the world" and "king of thieves" are not proper nouns but descriptions, and so require an article. But what gives you some leeway is that, to the average English-speaker's ears, specific titles can sound like proper names. So if you said

I am King of the World.

... as if that was your name, then you can get away without using an article and it doesn't sound particularly strange. Maybe there's some rule somewhere that says that that's right. I think it's wrong, but it doesn't sound jarring.

As I said, I'm having trouble finding a good authority on this. I did come across "The is used in place names and titles including of. In the case of official job titles, the is usually dropped if there is only one such incumbent at any given time." (Reference)

Solution 2:

I think this extract from the ‘Longman Student Grammar of Spoken and Written English’ might cover it:

When a predicative noun phrase names a unique role or job, either a zero article or the is used.

Solution 3:

The presence of the definite article shifts focus to itself from 'king':

"I am king of the world."

vs.

"I am the king of the world."