A more thorough explanation:

Definition: Contubernium is a Latin term used in Roman law to describe a marriage-like union between slaves. In the United States, contubernium was recognized before slavery was abolished, but only one Southern court gave a marriage between slaves legal effect upon manumission. In 1825, the Louisiana legislature passed a law expressly making such marriages invalid.

Example: Among slaves, there could only be contubernium, which was cohabitation of the sexes for a longer or shorter time, but it did not bring any civil rights. Cohabitation in a state of slavery was not marriage, or evidence of marriage. It conferred no rights upon the offspring, and created no legal disabilities on the part of the father from forming a valid marriage, whenever he became in a condition which would authorize him to contract one.

Explanation: The example illustrates that contubernium was a type of union between slaves that was not recognized as a legal marriage. It was a permitted cohabitation that did not confer any civil rights or legal disabilities on the parties involved. The example also shows that the father could form a valid marriage whenever he became free and in a condition to do so.