What Is a Contract?

Contract law begins with a deceptively simple question: when does a promise become legally enforceable?

People make promises constantly. Friends promise to meet for lunch. Parents promise rewards to children. Neighbors promise favors. Businesses promise delivery, payment, employment, repairs, financing, confidentiality, or future cooperation. Some promises matter morally or socially, but not every promise gives rise to legal liability. Contract law is the system courts use to decide which promises the law will recognize, enforce, excuse, interpret, or remedy.

A contract is commonly described as a legally enforceable promise or set of promises. That definition is useful, but it immediately raises several questions. What makes a promise legally enforceable? What if the parties disagree about what they meant? What if one party changes its mind? What if the agreement was oral? What if performance becomes difficult or impossible? What if the contract was unfair, vague, mistaken, or induced by pressure? What should the law do when a promise is broken?

These questions form the architecture of Contracts. The subject is not merely about memorizing rules. It is about learning a sequence of legal inquiries. A Contracts student must learn to classify problems: formation, terms, defenses, performance, breach, excuse, and remedies. Once that structure becomes familiar, even complicated fact patterns become manageable.

The first principle is that contract law does not enforce every promise. A social promise may create disappointment, but not damages. A moral promise may create personal obligation, but not legal obligation. A vague statement of hope, intention, or future willingness may influence behavior, but still fall short of contractual commitment.

For example, if Alex says to Jordan, “We should have dinner sometime,” no contract has been formed. The statement is too indefinite and social in character. It does not identify a clear bargain, definite performance, or legal commitment. If Alex fails to schedule dinner, Jordan may be annoyed, but Jordan does not have a contract claim.

Compare that with: “I will pay you $500 to repair my fence this Saturday,” followed by, “I accept.” That exchange has legal significance. It identifies parties, performance, price, and timing. It also reflects a bargain: money in exchange for repair work. If one party fails to perform, contract law may provide a remedy.

The difference is not that one promise is sincere and the other is not. The difference is that contract law asks whether the promise was made in a legally recognizable way. The law is concerned with commitment, exchange, reliance, commercial certainty, fairness, and remedies.

One of the first tasks in any Contracts problem is to identify the governing law. Contract law comes primarily from two sources: common law and statutory law.

The common law governs most contracts that are not for the sale of goods. This includes many contracts involving services, employment, land, construction, professional work, insurance, and other non-goods transactions. If a homeowner hires a painter, a client hires a lawyer, a patient hires a doctor, or an employer hires an employee, the agreement is generally governed by common law contract principles.

Article 2 of the Uniform Commercial Code governs contracts for the sale of goods. Goods are movable things at the time they are identified to the contract. Cars, refrigerators, lumber, crops, machinery, furniture, manufactured products, and electronics are goods. By contrast, legal services, medical services, employment, land, and insurance are not goods.

This classification matters. The common law and Article 2 often share broad principles, but they differ in important details. Article 2 is generally more flexible about formation, acceptance, contract modification, open terms, and gap fillers. The common law is often more formal, especially in areas such as mirror-image acceptance and modification.

Some transactions are easy to classify. A contract to buy a refrigerator is a sale of goods. A contract to receive medical treatment is a services contract. A contract to buy land is not governed by Article 2. A contract to purchase a truck is governed by Article 2.

Other transactions are mixed. A homeowner may hire a contractor to install custom kitchen cabinets. The transaction includes goods—the cabinets—and services—installation labor. A business may hire a company to design, manufacture, and install specialized equipment. A hospital may buy medical devices along with training and support services.

When a contract involves both goods and services, courts often use the predominant purpose test. Under that test, the court asks whether the primary purpose of the transaction is the sale of goods or the provision of services. If the main point of the deal is to obtain goods, Article 2 usually governs the entire transaction. If the main point is to obtain services, the common law usually governs.

Some courts use a different approach called the gravamen test. That test asks whether the dispute arises from the goods portion or the services portion of the transaction. If the problem concerns defective goods, Article 2 may apply. If the problem concerns negligent or inadequate services, common law principles may apply.

For beginning students, the key is not to memorize every variation. The key is to recognize that classification is an issue. If the facts involve both goods and services, say so. Then apply the predominant purpose test unless instructed otherwise.

Contracts analysis usually follows a life cycle. A contract is not just “made” and then “broken.” It develops through a series of legal stages.

The major stages are formation, terms, defenses, performance and breach, excuse, and remedies. This structure is the student’s map through the course.

Formation asks whether the parties reached a legally enforceable agreement. In the traditional model, formation requires offer, acceptance, and consideration.

An offer is a manifestation of willingness to enter into a bargain, made in a way that justifies another person in understanding that assent is invited and will conclude the deal. In simpler terms, an offer is a legally meaningful proposal. It gives the offeree the power to accept.

Acceptance is the offeree’s assent to the offer. Acceptance may occur through words, conduct, performance, or sometimes silence where circumstances justify treating silence as assent. The rules governing acceptance can differ between common law and Article 2.

Consideration is the bargained-for exchange. Each party must give or promise something of legal value. The law generally does not ask whether the exchange was economically equal. A bad bargain may still be a bargain. What matters is whether each side’s promise or performance induced the other.

Formation can also occur through substitute theories, most importantly promissory estoppel. Promissory estoppel may enforce a promise when the promisor should reasonably expect reliance, the promisee does rely, and enforcement is necessary to avoid injustice. This doctrine matters when a promise lacks traditional consideration but has caused serious reliance.

Once formation is established, the next question is terms. It is not enough to say, “There was a contract.” A lawyer must ask what the contract requires.

Terms may be express or implied. Express terms are stated in words, whether oral or written. Implied terms may arise from conduct, context, trade usage, prior dealings, or legal gap fillers.

Parties often leave things unsaid. They may agree on the basic deal but fail to specify delivery time, payment details, quality standards, or method of performance. Article 2 is especially willing to fill gaps when the parties intended to contract but left certain terms open. The common law may be less forgiving when essential terms are missing.

Interpretation becomes important when language is ambiguous. A term is ambiguous when it is reasonably susceptible to more than one meaning. Contract law then asks what the parties meant, often considering context, course of performance, course of dealing, and usage of trade.

Course of performance refers to how the parties behaved under the current contract. Course of dealing refers to how the parties behaved in prior transactions with each other. Usage of trade refers to practices or meanings regularly observed in a particular industry or market.

The parol evidence rule also belongs in the terms stage. In general, that rule addresses whether prior or contemporaneous statements may be used to add to, vary, or contradict a final written agreement. Students often find the rule difficult because it is not simply an evidence rule. It is a rule about the legal effect of a writing. If the parties reduced their agreement to a final written expression, earlier statements may be limited or excluded depending on the circumstances.

A contract may appear valid at first glance but still be unenforceable because of a defense. Defenses ask whether the law should refuse enforcement even though the ordinary requirements of formation may be present.

Common defenses include incapacity, duress, undue influence, misrepresentation, mistake, unconscionability, illegality, public policy, and the Statute of Frauds.

Incapacity concerns whether a party had legal ability to contract. Minors and persons lacking mental capacity may have power to avoid certain agreements.

Duress involves wrongful pressure that deprives a party of meaningful choice. Undue influence involves unfair persuasion, often in relationships involving trust, dependency, or dominance.

Misrepresentation occurs when one party makes a false statement that induces the other to contract. Mistake may arise when one or both parties are mistaken about a basic assumption on which the contract was made.

Unconscionability addresses extreme unfairness. It often involves both procedural concerns, such as unequal bargaining power or hidden terms, and substantive concerns, such as oppressive or one-sided provisions.

Illegality and public policy prevent enforcement of agreements that the law does not want to support. A contract to commit a crime is the obvious example, but public policy problems can also arise in restraints on trade, waivers, or agreements affecting important social interests.

The Statute of Frauds requires certain types of contracts to be evidenced by a writing signed by the party to be charged. Students should learn the common categories, including certain land contracts, contracts that cannot be performed within one year, promises to answer for another’s debt, and certain goods contracts above the applicable threshold.

If a contract is formed, its terms are identified, and no defense prevents enforcement, the next question is performance. What did each party have to do, and when did the duty come due?

Performance problems often involve conditions. A condition is an event that must occur before a duty becomes due, or that can cut off an existing duty. For example, a buyer’s duty to purchase a house may be conditioned on obtaining financing. If the financing condition fails, the buyer may not be in breach for refusing to close.

Breach occurs when a party fails to perform a contractual duty when performance is due. But not all breaches are equal. A material breach is serious enough to excuse the other party’s remaining performance. A minor breach may allow damages but does not necessarily discharge the other party’s duty.

Contracts exams often test whether a breach is material. Relevant considerations may include the extent of the deprivation, whether damages can adequately compensate, whether the breaching party acted in good faith, and whether the breach can be cured.

Performance analysis also includes substantial performance. Under common law principles, especially in construction and service contracts, a party who substantially performs may be entitled to payment minus damages for defects. Perfect performance may not be required unless the contract or governing law demands it.

Article 2 has its own distinctive rules, including the perfect tender rule, subject to important qualifications. Under that rule, a buyer may have rights when goods or delivery fail to conform to the contract. But students should remember that Article 2 also contains cure provisions and other flexible doctrines.

Sometimes a party does not perform, but the law may excuse performance. Excuse doctrines ask whether changed circumstances or other legal reasons relieve a party from a duty.

Impossibility may apply when performance becomes objectively impossible. Impracticability may apply when performance becomes extremely and unexpectedly difficult or expensive because of an unforeseen event. Frustration of purpose may apply when an unexpected event destroys the principal purpose of the contract, even though performance remains technically possible.

These doctrines are narrow. Contract law generally expects parties to bear ordinary risks. A bad market, increased cost, or regret is usually not enough. The key question is whether an unexpected event undermined a basic assumption of the contract in a way the law recognizes.

Excuse may also arise from the other party’s breach, failure of a condition, waiver, prevention, or anticipatory repudiation. If one party clearly indicates before performance is due that it will not perform, the other party may have rights before the time for performance arrives.

The final stage is remedies. Contract remedies are not primarily designed to punish. They are usually designed to protect the injured party’s legally recognized interest.

The standard remedy is expectation damages. Expectation damages aim to put the injured party in the position they would have occupied if the contract had been performed. In a simple buyer-seller case, this often means the difference between the contract price and the cost of substitute performance or market value.

Reliance damages aim to reimburse costs incurred in reasonable reliance on the contract. They may be useful when expectation damages are difficult to prove.

Restitution focuses on preventing unjust enrichment. It may require a party to return the value of benefits received.

Consequential damages compensate for additional losses caused by the breach, beyond the immediate value of the promised performance. They are often limited by foreseeability. Incidental damages cover reasonable costs incurred in dealing with the breach, such as arranging substitute performance.

Mitigation is also important. The injured party must usually take reasonable steps to avoid unnecessary loss. A party cannot let damages pile up when reasonable alternatives are available.

Liquidated damages are contractually specified damages agreed to in advance. They are generally enforceable if they are a reasonable estimate of anticipated or actual harm and not an unenforceable penalty.

Specific performance is an equitable remedy ordering the breaching party to perform. It is more likely when money damages are inadequate, such as in contracts involving unique property. It is less commonly available for ordinary service contracts because courts are reluctant to supervise personal performance.

Contracts exams usually tell stories. A professor may describe negotiations, oral promises, emails, forms, changing terms, partial performance, misunderstandings, market shifts, excuses, and damages. The student’s job is not to retell the story. The student’s job is to organize it legally.

A strong answer classifies issues. It identifies the governing law, analyzes formation, determines terms, checks defenses, evaluates performance and breach, considers excuse, and calculates remedies.

This framework should become automatic. It prevents students from writing scattered answers and helps ensure that major issues are not missed.

Consider a simple exchange. A homeowner says to a painter, “I’ll pay you $3,000 to paint my house next week.” The painter says, “I accept.”

This short conversation contains much of the course.

First, the governing law is common law because the primary transaction is a service: painting a house. Paint and supplies may be involved, but the homeowner is primarily buying labor and skill, not goods.

Second, formation appears present. The homeowner made an offer. The painter accepted. There is consideration because the homeowner promised money and the painter promised painting services.

Third, the terms include the parties, price, work to be performed, and timing. Some details may be missing, such as paint brand or exact start time, but the agreement is likely definite enough for enforcement.

Fourth, there are no obvious defenses in the basic facts. Nothing suggests incapacity, duress, misrepresentation, illegality, or a writing requirement problem.

Fifth, performance and breach depend on what happens next. If the painter appears and properly paints the house, the homeowner must pay. If the painter fails to appear, the painter breaches. If the homeowner refuses access, the homeowner may breach or prevent performance.

Finally, remedies depend on loss. If the painter fails to appear and the homeowner reasonably hires another painter for $3,800, the homeowner may seek $800 in expectation damages, assuming the substitute price is reasonable. That amount puts the homeowner in the position expected under the original bargain: a painted house for $3,000.

A contract is a legally enforceable promise or set of promises. Contract law does not enforce every promise; it asks whether the parties made a legally recognizable commitment, whether enforcement is appropriate, and what remedy should follow from breach.

The first step in any Contracts problem is identifying the governing law. Common law generally governs services, land, employment, construction, and other non-goods transactions. Article 2 governs sales of goods. Mixed transactions require special attention, usually through the predominant purpose test.

The life cycle of a contract provides the basic structure of the course. Formation asks whether there is offer, acceptance, consideration, or a substitute basis for enforcement. Terms ask what the parties agreed to. Defenses ask whether enforcement should be denied. Performance and breach ask whether duties came due and whether they were satisfied. Excuse asks whether nonperformance is legally justified. Remedies ask how the law should respond after breach.

The central lesson is that Contracts is a system. Once students learn the system, they can approach even complex fact patterns with discipline and confidence. The goal is not to memorize isolated rules, but to see how promises move through legal analysis from agreement to enforcement.