Cohabitation is an arrangement where people who are not married, usually couples, live together on a long-term or permanent basis. It is often associated with romantic or sexually intimate relationships. Cohabitation has become increasingly common in Western countries since the late 20th century, being led by changing social views, especially regarding marriage, gender roles, and religion. Here are some key points about cohabitation:

• Cohabitation can mean any number of people living together. To "cohabit," in a broad sense, means to "coexist".

• Cohabitation shares many qualities with marriage. Often couples who are cohabiting share a residence, personal resources, exclude intimate relations with others, and, in more than 10% of cohabiting couples, have children.

• Cohabitation can be an alternative to marriage in situations where marriage is not possible for legal or religious reasons (such as same-sex, interracial, or interreligious marriages).

• Cohabitation can have legal implications. For example, a cohabiting partner may have fewer rights than a married partner in terms of inheritance or property rights.

• Cohabitation can be protected by a cohabitation agreement, which is a voluntary, signed agreement that allows couples to specify the day-to-day joint financial arrangements of their relationship. This agreement can also specify how to separate assets, such as shared property, should the relationship come to an end.

• Cohabitation is often seen as a step towards marriage. Most married adults who lived with their spouse before they were married saw cohabitation as a step towards marriage when they first started living with their now-spouse.

• Cohabitation is acceptable, even for couples who don’t plan to get married, according to a new Pew Research Center survey. Even so, a narrow majority says society is better off if couples in long-term relationships eventually get married.

• Cohabiters who have gotten engaged since moving in with their partner are more likely than those who are not currently engaged to say they saw living together as a step toward marriage.

• Adults younger than 30 are more likely than older adults to see cohabitation as a path to a successful marriage.

In summary, cohabitation is an arrangement where people who are not married, usually couples, live together on a long-term or permanent basis. It can have legal implications and can be protected by a cohabitation agreement. Cohabitation is often seen as a step towards marriage, and younger adults are more likely to see it as a path to a successful marriage.