WA, dear Waseem Saheb,
You have a good question.
There is no parallel word for DEEN in any language. As you know it means THE SYSTEM OF LIFE.
In QXP, I did make a subtle distinction by using small r for religion = mazhab and capital R for Religion = DEEN.
The ancient meanings remain unchanged as you see below.
The Quran & Hadith use Deen even for the system of life: among non-Muslims - Deenil Aghiaar, in a kingdom - the king's Deen - Deenil Malik, mazhab of the ancestors = Deenil Aaba and of the idol worshipers - Deenil Mushrikeen. In these cases, it will merely mean THE SYSTEM OF LIFE.
Following the context, DEEN of Allah = DEENILLAH = ISLAM = The Divinely Prescribed System of Life.