DIIN- Lexicography
"Ad-Diin": The Recompense, The Requital, The Judgement
"Diinun": Religion, religious worship or doctrine, belief, obedience, submissiveness, piety, custom, habit, Judgement, Sentence, Requital. (Wortabet)
Affair, Religious law, Godliness, Compulsion, Victory, Power, Authority, Management. (J.G.Hava)
Benefit, Judge hard Upon. (F.Steingass)
Other shades of meaning and derivatives of the root word:
"Diinah”: Maturity of a debt, obedience
"Dayyaan”: The Rewarder (God), Judge. (J.G.Hava)
Requiter, Administrator, Manager, Ruler
"Madyunun": Indebted, Debtor. (Wortabet)
"Dayan”: Debtor, Creditor, Debtee
"Madyin”: Judged, slave. (J.G.Hava)
"Diinun”:

1. Judgement: "Owner of the Day of Judgement"
2. Religion: "And the Religion is for Allah (Alone).
3. Law: "He (Yusuf) was not to take his brother, by the law of the king:
4. Obedience:"Worship you, Allah (Alone), making, exclusive for Him in the obedience".

"Lo, for Allah is the obedience exclusively ".

"Diinun" is primarily "obedience". (Vocabulary of the Holy Quran, Dr Abdullah Abbas Nadvi)
"The term (Diin) has connotations of indebtedness and obligation, i.e., of the believer's duties towards God. In Islamic theology `Diin' comprehends both `faith' (Imaan), and the practice of the prescriptions of the law, the Shariia, and is often contrasted with duniyaa, the sphere of secular life ." (Dictionary of Religions, John R. Hinnells.)