Ancient laws didn’t come with definition sections.
When you see some of the lengthy, arbitrary and self-contradictory definitions in modern legal codes, this may at first seem like a feature rather than a bug, but it still leaves the modern reader of the Law of Moses struggling with certain ambiguities, not least the ones concerning marriage.
This was not a problem for the people who lived under the Law of Moses in ancient times. They understood the sociocultural environment in which the law was given well enough to obey God’s commands without the need for the endless paragraphs of legalese modern lawyers generate like spiderwebs.
The bad news is that understanding the background of the law wasn’t their problem; keeping it was.