I don't mind the word slave - depending on the circumstance. Let's say a thief was caught stealing. If he can't pay back what he stole - he becomes a slave to pay off his debt. Or let's say there is a daughter that has a boyfriend. That boyfriend took her virginity, and simply left. Well that man owes a hefty bride price to her father, since he took her virginity. He can't afford it? Then he becomes her father's slave until that debt is paid off.
And let's not forget - in the new testament writings of the apostles - you'll see them start off their letter's like this:
Romans 1:1
This letter is from Paul, a slave of Christ Jesus, chosen by God to be an apostle and sent out to preach his Good News.
Slavery was not like what happened in the states a while ago. They are still guaranteed a sabbath day's of rest. Also, it's a limited time-frame and there are further protections:
Exodus 21:27
And an owner who knocks out the tooth of a male or female slave must let the slave go free to compensate for the tooth.
Ephesians 6:5-9
5 Slaves, obey your earthly masters with deep respect and fear. Serve them sincerely as you would serve Christ. 6 Try to please them all the time, not just when they are watching you. As slaves of Christ, do the will of God with all your heart. 7Work with enthusiasm, as though you were working for the Lord rather than for people. 8Remember that the Lord will reward each one of us for the good we do, whether we are slaves or free. 9 Masters, treat your slaves in the same way. Don’t threaten them; remember, you both have the same Master in heaven, and he has no favorites.