Detrimental reliance, also known as "promissory estoppel", is a legal concept whereby one party has a legal duty to fulfill obligations under the terms of a contract (written or oral) in order to prevent the other party from experiencing an unjust loss. In other words, this principle can be used to enforce a contract if an obligated party does not want to fulfill its responsibilities. In ordr ot prevail in such a claim 5 elements must be proven: (1) a promise was made; (2) there was actual reliance on the promise; (3) such relaince was reasonable and/or forseeable; (4) the reliance was detrimental (i.e. a harm was suffered); and (5) an injustice can only be prevented by enforcing the promise.