Express contract; promises communicated by language

 

(1)  offer

(2)  acceptance

(3)  consideration (or a substitute)

(4)  no defenses to formation

 

Implied contract; parties’ conduct indicates that they assented to be bound

 

(1)  offer

(2)  acceptance

(3)  consideration (or a substitute such as promissory estoppel/detrimental reliance); promissory estoppel requires showing that (a) promisor should reasonably expect his promise to induce action or forbearance, (b) induced action or forbearance is of a definite and substantial character, and (c) such action or forbearance is in fact induced.

(4)  no defenses to formation

 

 

Quasi-contract; one party is unjustly enriched at the expense of the other party, so that the enriched party must pay restitution to the other party equal to the unjust enrichment; there is no contract; one party can recover benefit conferred to other party to avoid unjust enrichment;

 

(1)  One party conferred a benefit on the other by rendering services or expending properties

(2)  The conferring party had a reasonable expectation of being compensated

(3)  The benefits were conferred at the express or implied request of the other person

(4)  Unjust enrichment would result if the defendant were allowed to retain the benefits without compensating the plaintiff