DICT.TW Dictionary Taiwan

 con·cu·bi·nage /kɑnˈkjubənɪʤ, kən-/
 非法同居,納妾

 Con·cu·bi·nage n.
 1. The cohabiting of a man and a woman who are not legally married; the state of being a concubine.
 Note: ☞ In some countries, concubinage is marriage of an inferior kind, or performed with less solemnity than a true or formal marriage; or marriage with a woman of inferior condition, to whom the husband does not convey his rank or quality. Under Roman law, it was the living of a man and woman in sexual relations without marriage, but in conformity with local law.
 2. Law A plea, in which it is alleged that the woman suing for dower was not lawfully married to the man in whose lands she seeks to be endowed, but that she was his concubine.
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 concubinage
      n : cohabitation without being legally married