1. A small circle of metal that you wear on your finger as an ornament or to show that you are engaged or married. It often has a diamond in it. English = diamond ring, engagement ring, wedding ring.
2. An agreement that two people have made with each other to get married. English = engagement.
3. The man to whom a woman is engaged to be married; the woman to whom a man is engaged to be married. English = fiancee; fiance.