A man and a woman (or in some cases the same sex people) staying together in the same house or at same address for certain long period of time, as if they were married , though not, is known as Cohabitation. The court assumes that they are having a sexual relationship as well as a married couple would. There are certain rights and regulations given by the court to such unmarried couples. There may be several reasons for these couples to stay as a single yet living together as if married to one another. Some states do not allow such relationship and term it as criminal offence under adultery law.