An excerpt from professor Alexei Osipov's book "The Search for Truth on the Path of Reason", published in English and Russian. (Osipov is a well known Russian Orthodox theologian, professor and lecturer from Moscow Orthodox Theological Seminary):
There are several different points of view about the derivation of the word “religion” (from the Latin word religio, meaning conscientiousness, piety, reverence, religion, holiness, service to God). Thus, Cicero, the famous Roman orator, writer, and political activist of the first century B.C. considered that this word came from the Latin verb relegere (meaning, to gather again, to re-consider, to set aside for a particular use), with a connotative meaning of “showing reverence” or “relating to something with particular attention or respect.” Proceeding from this, Cicero sees the very existence of religion as reverence before the higher powers, before the Divinity. This thought of Cicero’s assuredly shows that piety is one of the most important elements of religion, without which religiosity becomes sanctimoniousness, hypocrisy, and empty ritual; and belief in God becomes no more than cold, lifeless doctrine. At the same time, we cannot agree with the statement that reverence toward something mysterious, even toward God, comprises the essence of religion. No matter how great and necessary piety is to religion, it is nevertheless only one of the feelings present in man’s religious relationship to God, and does not express its essence.
The famous Western Christian writer and orator Lactantious (†330) considered that the term “religion” comes from the Latin verb “religare,” which means “to bind, to join.” Therefore he defines religion as a union of piety between man and God. “With this condition,” he writes, “we are born in order to show a just and dutiful submission to the Lord Who has given us being; to know only Him, to follow only Him. Being bound by this union of piety, we find ourselves in union with God, from which religion has received its name. ‘Religion’ comes from the union of piety by which God has bound man with Himself….”
Lactantious’ definition reveals the very essence of religion—a living union of man’s spirit with God, which takes place within the secret chambers of the human heart.
Blessed Augustine (†430) similarly understood the essence of religion, although he considered that the word “religion” comes from the verb “religare” meaning “to come together,” and that religion itself indicates a coming together, the renewal of a once lost union between man and God. “Seeking this,” he writes, “or rather, seeking out again (from which apparently it has received the name ‘religion’
, we yearn towards Him with love, so that once we attain it, we will be at peace.”
Thus, the etymology of the world “religion” points to its two basic meanings: unity and reverence, which explain religion as a mystical spiritual union: a living, reverent unification of man with God."
Sergei Bulgakov (†1944), the great Russian thinker and later theologian, expressed this thought in the following words:
"Religion is [a process of] acquiring the knowledge of God, and the experience of a connection with God."
PS You can find Osipov's books (in Russian and English) at his website.
goo.gl/pDXcWU
goo.gl/GI4hCJ
PPS Generally, I like Prof. Osipov's books, But please be careful. When you start reading his books, you have to filter his thoughts and ideas. Some of them do not sound Orthodox. For example, he is against infant baptism. God bless.