Word for "translating" English to English

I would describe the process of transforming a text written in a source language (e.g. Old English) that is largely unintelligible to readers of the target language (in this example, modern English) as translation.

Adaptation could refer either to the transformation of the work from one medium or format into another (e.g. the transformation of a novel into a screenplay), or to the rewriting of a text for a different audience (e.g. the simplification of a story first written for adults in order to make it easier for children to read).

Turning an archaic or old-fashioned text that is still largely intelligible in its original form into contemporary language is modernization or updating -- though the term revision has also been applied to modernized versions of the Bible in particular.

In my opinion, modernization would be the most appropriate term to describe the updating of the English of a text written by John Locke into modern English.

To render Text A into Text B is a general term that could be applied to any of these transformations (as too is the verb transform, of course).

What a fantastic question! I've always wondered this.

if Locke's philosophies were rewritten point by point in contemporary English...

.. what marketing term would be used on the cover?

So, James Frey is going to { whatever term } Locke's philosophies in to modern English. What would it say on the cover?

I think rendered or re-written would be best.

I feel adapted is not really right because it has a specific clear and common use, in the field and the entertainment field generally, which is different. I fear modernization or updating could be interpreted as merely "fixing the spelling" ... making fairly small changes.

You're talking about a literary "cover-version", or perhaps "remix", or somewhere between the two.

Re Shakespeare, I've wondered if someone has done this? And just what word would be best there. (As you go back further in time, plain "translation" is more fitting.)

Note that "in" could be useful in certain descriptions: For example, an excellent title for the book you describe could be:

"John Locke in Modern English"

Note that a similar problem, to the problem you describe, comes in translating verse. So, the various translations of Homer etc are more often described as "versions of" or the like. A further example is "translating" pop songs, a very arcane field. In that extreme case it's "nothing like" translating, the writer in question just has to write a totally new song, in English, that ideally has somewhat the same meanings, feelings. (You'd almost certainly just say "the XYZ version", it's not a translation.)

The Bible has been translated into various languages. Bible Gateway considers the list as versions