What is a Bilateral Contract?

A bilateral contract consists of two promises between individuals that form a contract. Specifically, one party makes a promise to another party that she will do something (or forgo doing something) in exchange for the other party's promise to do something (or promise to forgo doing something).

• Example: Eric promises to wash Julia's car if she promises to pay him $20. The both activities will occur at some point in the future, so you have two promises of future performance.

What is a Unilateral Contract?

A Unilateral contract is an agreement with only one promise. That is, one party promises a future action if the other party performs whatever is requested of her. The promising party does not want a return promise. As such, a contract is formed or comes into exists once the other party begins to perform the requested services.

• Example: Suppose Eric tells Julia that he will pay her $20 if she washes his car. Eric does not want a promise to wash the car. Julia can accept Erics offer by beginning to wash his car. Julia is not obligated to wash the car unless or until she begins doing so. Further Eric is not obligated to pay Julia until she begins washing the car.
• Note: The common characteristic between unilateral and bilateral contracts is that it entails a promise of performance and a demand from the offeree. This is critical to the requirement that a contract contain an offer, acceptance, and exchange of value.

Related Topics

• Contract Law (Intro)

• What is a Contract?
• Contract Theory Definition
• Meeting of the Minds
• Doctrine of Utmost Good Faith 
• Aleatory Contract Definition
• What are the sources of contract law?
• Restatement of Contracts
• Uniform Commercial Code
• Convention on Contracts for the International Sale of Goods (CISG) 

• What is a Unilateral Contract vs a Bilateral Contract?
• What is an Express Contract vs an Implied Contract?
• What are the requirements to form a Contract (Offer, Acceptance, Consideration)?
• What is an Enforceable Contract vs. a Valid Contract?
• What is a Void Contract vs a Voidable Contract?
• Adhesion Contract 
• What is Mental Capacity to contract?
• What is the requirement of a Lawful Purpose?
• What are common types of Voidable Contract?

• What is an Offer?
• Sum Certain (Contracts) Definition

• When does an offer to contact terminate?
• Counterparty Definition
• Mirror Image Rule?
• Rule for Sale of Goods
• Silence is Not Acceptance?
• Mailbox Rule
• Shrink-wrap Agreement Definition
• Click-Wrap Agreement Definition
• What is Consideration?
• What is Promissory Estoppel?
• When is a contract required to be in writing Statute of Frauds?
• What type of writing satisfies the statute of frauds?
• Exceptions to the Statute of Fraud
• Documents Under Seal
• Who Can Sign Contracts on Behalf of a Company?
• E-Sign Act
• Privity of Contract
• Who are third-party beneficiaries to a contract?
• What is assignment and delegation of a contract?

• When is a party's Duty of performance?
• Aleatory Contract
• What is an Executed contract vs an Executory contract?
• Inchoate Definition
• Evergreen Contract

• What is Performance, Substantial Performance, and Breach of a contract?
• What is performance of a Divisible Contract?
• When is a party's duty of performance discharged?
• What are conditions to Contract (Precedent & Subsequent)?
• Abandonment Option (Contract) Definition
• Cooling Off Rule Definition
• What is tender performance of a contract?
• What are Impossibility and Impracticability
• What is a Frustration of Purpose?
• Waiver or Release from Contract
• Accord and Satisfaction
• Force Majeure Clause
• Novation
• What is a Breach of Contract?
• Repudiation (Contract) Definition
• Anticipatory Repudiation
• Acceleration Clause (Contracts) Definition
• What methods exist for resolving a breach?
• Assumpsit
• What remedies exist for a breach of contract?
• Rescission (Contract)
• Exculpatory Clause
• Hold Harmless Clause
• What is Efficient Breach?
• Organization of a Contract
• How to Read the Contract
• Boilerplate
• Contract Representations & Warranties
• Contract Covenants
• What rules does a court follow in interpreting a contract?
• Addendum 
• Allonge Definition
• What is the Parol Evidence Rule?
• What is a complete integration vs a partial integration?
• Exceptions to the Parol Evidence Rule
• Patent and Latent Ambiguity in a Contract
• Service Level Agreement Definition 
• Offtake Agreement