What is marriage?

Marriage, with a basic definition, is two people's uniting their life. They know each other in time, and they decide to be a family. After marriage, a person's family is not the family he/she got since his/her born anymore. After the incident the spouse is the new family. They live, sleep and eat together. They do the most of things together. And we can understand the 'uniting lives' idea from that.