分居是指伴侣停止同居生活。主要原因有三：1)正处理离婚手续、2)为婚姻关系增加前景、及3)增进婚姻关系。有专家指出6个月的分居是最佳的时间长度，因为这段时间足够创建第二个住家和透视婚姻前景，但不足够作为永久分开。分居可以非正式进行，但亦可以透过分居协议以开展合法分居。在华语地区而言，分居一词主要指单方面申请离婚手续后的一段时间，而在美国多数州份如维珍尼亚州亦然。

Marital separation occurs when partners to a marriage stop living together. The three main reasons why couples separate are (1) as a step in the divorce process, (2) to gain perspective on the marriage, and (3) to enhance the marriage. Some experts regard a six-month separation as good amount of time for a temporary separation, since it is long enough to set up a second household and gain perspective, but not long enough to seem permanent. A separation can be initiated informally, or there can be a legal separation with a formal separation agreement. Many U.S. state statutes, for example Virginia's, specify that being separated for a given period of time can be grounds for divorce.