The derivation by idiom, the word al-deen is derived from the third class verb 'daan' which sometimes contracted with itself and sometimes with the letter 'laam' and sometimes with the letter 'baa' and shifting the meaning with the contraction with it. Thus when being contracted with itself it will become 'daanuhu' synonymous to the meaning 'malakuhu' which means His possession, His account, His subjugation, His tribute and His system.
And when it is attached with the letter 'laam' as in 'daana lahu', the meaning something which is submitting to Someone and obeying Him. And when attached with the letter 'baa' and it becomes 'daana bihi' with the meaning adopting a religion or a doctrine and living through its application in ones life, and behaves with it, and believes in it, and this idiomatic meaning for 'the deen' that exists in 'the deen' for terminological derivation as will be seen in the following statement. 'The deen' is something which makes its follower invincible, with only His teachings, and His laws, as it includes the submission of the worshipers to the One which is worshiped and directing worship to His sole Essence. And the worshiper performing worship with psychological motives. He adheres to the 'deen' without any coercion or without any force.
The deen as per technical meaning refers to, "the changing in the definition of the deen in terminological term, where every person knows it by its drinker, and he does not see that indeed the importance of the specifications of the deen. And among them those who know it as it is the path of the God received through the way of revelation. And many Muslims only know about this definition shortly to refer to the "celestial" religion only.
Together with this indeed, whatever which has been adopted by man-kind and whatever that they worship is known with the term "deen" whether it is valid or invalid. The God the Highest mentions as recorded in the Glorious Quran which means, "And whoever follows other than Islam as his religion, thus he is not accepted and in the hereafter he is among the losers" (Surat Aali-Imran vs. 85). And in the al-Kaafirun vs. 6, "And for you is your religion, and for me is my religion".
And the God the Highest named those polytheists among the Arabs as among the followers of heathen religion and their way of life clinging to ethnocentrism. The Arabs during spiritual ignorance period were the nation with no revealed scripture. Some non-Muslims are specializing in the area of morality as what has been mentioned by Rudolph Eucken, "Indeed the religion contains recognition on our responsibilities and duties through divine commands". Some non-Muslims specializing in the area of reasoning, logic and meditation. Rudolph Eucken said, "The religion is mystical experience which outreaches the human-being and in it, there are contradictions of the life".
Other definitions that we could see from the angle where we leave behind the height of several angles and referring to the definition as it says, "The religion is the belief and trust in the Sacred Essence and the assembly of followers of the pathway who submit themselves to the Essence in awe with passionate love and full of humility". This definition includes the worshiper who enslave themselves to the God the Highest or to other entities. This definition refers to the belief be it of those who worship the God the Highest for example Islam, or the previous religions that had undergone long historical period such as Judaism, Christianity and refers also to major religions at the position of non-celestial belief for example Hinduism, Buddhism or all other pagan beliefs.
As for the definition to explain the case of worshiper or people who believe in a religion, then not a must for him to submit himself with humility or with intense love to the one who is worshiped in term of acts of worship. For the "worship", there are other definition which aims at the worshiper in term of his worship acts whether he is worshiping together in awe, with full of love and humility to the one who is worshiped since that is what had been seek by the sons of Adam in their worship. And the God the Highest knows well about the matters of the universe.
Sealed with prayers for mercy, peace and love, amin!