Meaning of the then king

Question

Meaning of the then king according to my book is

The king then reigning

Can I say

The king reigning then

Is there any difference. Is there any rule governing the position of then

Answer 1

The use of “then” here is an adjective, and sounds better before the verb. They’re both pretty much the same as far as meaning goes.

Also, other ways you can say this:

• “The king reigning during that time”
• “The king reigning at that time”

Answer 2

The then king

It is a Noun Phrase (NP) with the head noun being king, The preposition then along with the head form a Nominal.

The structure of the NP is like this:

DETERMINER _{(realized by a DETERMINATIVE)} + [Pre-Head MODIFIER _{(realized by a PREPOSITION)} + HEAD _{(realized by a NOUN)}]

The part inside the [...] is called Nominal.

Both the king then reigning... and the king reigning then... are correct. But they are not complete sentence.