There are numerous definitions of religion and only a few are stated here.

Peter Mandaville and Paul James define religion as "a relatively-bounded system of beliefs, symbols and practices that addresses the nature of existence, and in which communion with others and Otherness is lived as if it both takes in and spiritually transcends socially-grounded ontologies of time, space, embodiment and knowing". This definition is intended, they write, to get away from the modernist dualisms or dichotomous understandings of immanence/transcendence, spirituality/materialism, and sacredness/secularity.
Urarina shaman, Peru, 1988

Edward Burnett Tylor defined religion as "the belief in spiritual beings". He argued, back in 1871, that narrowing the definition to mean the belief in a supreme deity or judgment after death or idolatry and so on, would exclude many peoples from the category of religious, and thus "has the fault of identifying religion rather with particular developments than with the deeper motive which underlies them". He also argued that the belief in spiritual beings exists in all known societies.

The sociologist Durkheim, in his seminal book The Elementary Forms of the Religious Life, defined religion as a "unified system of beliefs and practices relative to sacred things". By sacred things he meant things "set apart and forbidden—beliefs and practices which unite into one single moral community called a Church, all those who adhere to them". Sacred things are not, however, limited to gods or spirits. On the contrary, a sacred thing can be "a rock, a tree, a spring, a pebble, a piece of wood, a house, in a word, anything can be sacred". Religious beliefs, myths, dogmas and legends are the representations that express the nature of these sacred things, and the virtues and powers which are attributed to them.

When religion is seen in terms of "sacred", "divine", intensive "valuing", or "ultimate concern", then it is possible to understand why scientific findings and philosophical criticisms (e.g. Richard Dawkins) do not necessarily disturb its adherents.

An increasing number of scholars have expressed reservations about ever defining the "essence" of religion. They observe that the way we use the concept today is a particularly modern construct that would not have been understood through much of history and in many cultures outside the West (or even in the West until after the Peace of Westphalia).

Information Source: https://en.wikipedia.org