What term describes an agreement that is enforceable by law?

The term that describes an agreement that is enforceable by law is "contract." A contract is a legally binding agreement between two or more parties, which creates mutual obligations that are enforceable in a court of law. For a contract to be valid, it typically must contain certain essential elements such as offer, acceptance, consideration (something of value exchanged), and the intention to create legal relations.

In contrast, terms like "arrangement," "agreement," and "understanding" might imply a meeting of minds or some form of consensus, but they do not necessarily carry the enforceable weight in a legal context. An arrangement may lack the formality required for legal enforceability, and an understanding might be too vague or informal to warrant legal action. An agreement, while it suggests that parties have come to some sort of agreement, does not inherently imply that it possesses the legal enforceability like a contract does.

Thus, the specificity and formality associated with a contract are what make it distinct as a legally enforceable agreement.