A more thorough explanation:

Plagium is a term used in Roman law to describe the act of kidnapping, specifically of a slave or child. This also includes the act of harboring someone else's slave. It is also known as crimen plagii.

• If someone were to take another person's slave and keep them for themselves, that would be considered plagium.
• If a child were to be taken from their parents and kept against their will, that would also be considered plagium.

These examples illustrate how plagium involves the act of taking someone else's property (in this case, a slave or child) and keeping them without their consent. It was a serious crime in Roman law and was punishable by severe penalties.