Working for survival obligations like room and board bills with little or no choice on vocational, entertainment or familial matters. Slaves in ancient Egypt were often ordered to marry another with or without their own consent.

In ancient Greece a professional scribe, considered a very prestigious job back then could find himself picking crops/digging ditches for 14 hours a day for his remaining days if he gambled beyond his means and ended up bankrupt.

Or if you were part of a wealthy family and were cut off, one would end up having to find a master persuade them to take you on as a slave and then earn your way out of it to have a fair place in society again.

While customs have differed over the eons the lack of choice and expectation of extreme servitude was the essence of slavery. This has been abandoned today, mostly.

Many cultures and most religions still have this as a way of life. Utter servitude.

How many wives has Jesus had now if each nun was a wife of him.

Imagine what that meant back in the day 2000 years ago. If you joined his following then he would automatically have bedding rights to your wife.

To this day this view is still predominate. People kneeling in front of a priest asking for forgiveness.

Muslims expect servitude from their women as much as Catholics. War brides often end up with little or no life above that of slave. Some men take free minded liberal women and effectively turn them into slaves. As many women are so down on weak men that they end up almost as slaves.

If your working to pay  only your rent bills and vitals and have little or no choice on family or vocation then you are in effect a modern day slave.

The rise in human trafficking and behavior of some religions with their demand for servitude are in effect modern day religious/commercial slavery.

The fluff may have different names the result is the same.