FRCP 18 Joinder of Claims: Allows a party who has made a claim against another to join further claims with it against the same opponent. It authorizes claim joinder without limitation, regardless of whether the claim to be joined is related to the pre-existing claims or not, as long as the joined claim satisfies subject matter jurisdiction requirements.

Compulsory (must be brought)

Permissive (can wait)

STO (core of operative facts)

FRCP 13(g): Crossclaim (claim against co-party)

No STO, independent basis for SMJ.Yes STO, supplemental jurisdiction.Logical Relationship Test (core of operative facts, STO)FRCP 13 Counterclaim (claim against opposing party)By DefendantBy PlaintiffJOINDER OF CLAIMS