A more thorough explanation:

Definition: De magna assisa eligenda is a legal term in Latin that means "of choosing the grand assize." It refers to a writ that orders a sheriff to summon four knights to give oaths before the justices of assize. These knights then choose 12 more knights to form a grand assize, which determines who has the right in a writ of right.

One example of de magna assisa eligenda is when a landowner brings a writ of right against someone who claims to own their land. The writ of right is a legal action that allows the landowner to prove that they are the rightful owner of the land. The writ of right is heard by a grand assize, which is chosen through the writ of de magna assisa eligenda.

Another example is when a person is accused of a crime and demands a trial by jury. The writ of de magna assisa eligenda is used to select the jurors who will hear the case and determine the person's guilt or innocence.

These examples illustrate how de magna assisa eligenda was used in medieval England to select a grand assize, which was a group of knights who would determine the outcome of important legal cases.