What is religion?

This question hasn’t been asked since 2009, so I thought I’d do it again.

There is a professor at my university who is writing a book on this topic. He tells me that there are hundreds of different definitions and they cover all kinds of territory. Just for example, there is the issue of whether a religion must have a god (or gods).

So this is about you. Please refrain from saying any particular definition is right or wrong. Just tell us what your idea of religion is. What does it include for you?

And please also refrain from critiquing anyone else’s idea of religion—at least until we have ten different definitions. Critiquing tends to stop other people from throwing a hat in the ring. I just want to get a lot of different ideas so I can understand the territory people are living in.