The prerequisite is in compliance with monogamy and other imperative rules of law; the essence is an interdependent living unit in terms of love, economy and sex, but not in the form of marriage; the appearances and causes of nonmarital cohabitation varied. 其前提是不违反一夫一妻制和其他法律强制性规定;其实质是以非婚姻的方式在感情、经济和性等方面形成了相互依赖的生活共同体;其表现形态和形成原因多种多样。