Where do you draw the line between vanilla and kinky/bdsm sex?

I was wondering, what do you consider as vanilla and when does vanilla transition into bdsm? My husband and I had a little moment some time ago discussing it and I was surprised that we were not on the same page. So I thought I’d bring it up here to see how different (or similar) our views are.

Edit: Thank you for all your answers so far! I think it’s so interesting how different but also similar some views are. There are so many aspects that I did not think about or didn’t cross my mind and I am in fact more on my husband’s side of things now.

Of course, you don’t have to draw a line or if you don’t like to give your preferences a name and just want to enjoy it, that is totally fine. I personally like to categorize and name things to give myself some clarity.