What does “claims arising out of a common nucleus of operative fact” mean in joinder?

The phrase "claims arising out of a common nucleus of operative fact" refers to claims that are closely connected and originate from the same set of facts or circumstances, typically related to the same event or transaction. This concept is crucial in the context of joinder and supplemental jurisdiction because it allows for efficiency in litigation by permitting parties to resolve related claims in a single legal proceeding.

When claims share this common nucleus, it often indicates that they will likely involve overlapping evidence, witnesses, and legal issues, making it more practical to address them together. This can save both the court's time and the parties' resources by preventing the need for multiple lawsuits that could lead to inconsistent rulings.

Other choices, such as unrelated claims or separate filings, do not capture the essence of this legal principle, as they imply a lack of connection between the claims or require a more fragmented approach to litigation. In summary, claims that arise from the same event or transaction are characterized by their interconnectedness and relevance to one another, which is why the correct answer highlights their factual relationship.