A villein was a kind of farm worker in Europe in the Middle Ages, roughly from a thousand years ago to about five hundred years ago. A rich lord owned a large piece of land. He let a villein use a small part of it — a field to grow food on, a small house — and in return the villein had to work the lord's own land for a set number of days, hand over part of the harvest, and pay fees at certain times. Here is the part students find hardest to believe: the villein was not a slave, but he was not free either. He could own things, he could go to court, he could not be bought and sold on his own like an object. But he could not leave. He could not move to another village, marry, or send his son away to learn a trade without the lord's permission. And if the lord sold the land, the villein went with it — he belonged to the land, not to a person. So he sat in the middle, between a slave and a free farmer, and most of the people in medieval England lived exactly there. This is a history word. You will meet it in history books and museums, not in conversation, and it is rare enough that many native speakers do not know it. It sounds exactly like villain, which is not an accident — they are the same word, split in two. English spelled it both ways for centuries and then, quite late, gave the -ein spelling to the farm worker and the -ain spelling to the evil person in the story.

（中世紀的）農奴、隸農（台灣歷史課本多用「農奴」；嚴格說他不是奴隸，是「依附於土地的佃農」）