cohabitation
  同居
  Co·hab·i·ta·tion n.
  1. The act or state of dwelling together, or in the same place with another.
  2. Law The living together of a man and woman in supposed sexual relationship.
     That the duty of cohabitation is released by the cruelty of one of the parties is admitted.   --Lord Stowell.
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  cohabitation
       n : living together (as spouses) [syn: living together]