Definition - What does Legal Fiction mean?
Legal fiction refers to a legal decision or ruling that is not based on actual facts, but is instead based on hypothetical/fictional information.
Adoptive parents gaining the rights of parents as if the child is their own offspring is an example of legal fiction.
Justipedia explains Legal Fiction
The reason why legal fiction exists is because it makes it much more convenient and efficient for the courts to do certain things. So, if the court can simply cite legal fiction for certain circumstances—instead of having to go through the details of why certain facts may not exist—but the laws still apply, then it can save a lot of time.
Legal fiction is also commonly used in the law of wills and testaments.