When contract language is unclear, judges do not simply guess what the parties intended. They apply a set of interpretive rules — called canons of construction — that have been developed over centuries of common law and are now widely recognized across American courts. These canons are tools of legal reasoning, not magic formulas, and different canons sometimes point in different directions. But knowing what they are and how they work gives business owners a significant advantage both in drafting contracts that say what they mean and in evaluating disputes when language is contested.
The canons of construction are often described as Latin maxims, which can make them sound arcane. But the underlying principles are sensible and practical. Most of them reflect ordinary reasoning about how language works and what drafters are likely to have intended. You probably apply versions of several of these canons in your own reading of contracts, without knowing their formal names. Giving them names simply makes the reasoning more systematic and predictable.
Ejusdem Generis: General Terms Are Limited by the Specific Terms Around Them
Ejusdem generis — Latin for ‘of the same kind’ — is one of the most frequently invoked canons in commercial contract disputes. It provides that when a general term follows a list of specific items, the general term is interpreted to be limited to things of the same category or class as the specific items. The general term does not extend to everything in the universe of that word’s ordinary meaning; it is bounded by the class established by the preceding specifics.
A business example makes this concrete. Suppose a commercial lease prohibits the tenant from using the premises for ‘retail sales, restaurant operations, entertainment venues, or any other commercial activity.’ A dispute arises about whether operating a small professional services office — a dental practice, say — is a ‘commercial activity’ within the prohibition. Under ejusdem generis, a court would likely find that ‘any other commercial activity’ means activities of the same general type as the preceding list: high-traffic, public-facing, consumer-oriented businesses. A private professional office might not fall within that class.
The practical lesson for drafting is twofold. If you want your general term to sweep broadly and include things unlike the specific items listed, say so explicitly. Language like ‘including but not limited to the following examples’ or an explicit statement that the list is non-exhaustive can help, though courts will still consider context. Conversely, if you want your catch-all to be genuinely limited to things similar to the specific items, the ejusdem generis canon works in your favor as a drafting backstop, but explicit language defining the class is always cleaner.
Ejusdem generis applies most strongly when there is a recognizable category that the specific items share. If the preceding list is so heterogeneous that no common class can be identified, courts may decline to apply the canon and give the general term its broader ordinary meaning. This is another reason why precision in drafting lists pays dividends: a well-defined set of specific items makes the class apparent and makes the canon’s application more predictable.
Expressio Unius: Naming Some Things Excludes Others
Expressio unius est exclusio alterius — ‘the expression of one thing is the exclusion of others’ — is a related but distinct canon. It provides that when a contract expressly includes certain items in a list or category, things not included are presumed to be excluded. Enumerating specific things implies a deliberate choice not to include things omitted from the enumeration.
Consider a contract that gives one party the right to audit the other party’s ‘financial records and accounting systems.’ A dispute arises about whether this right extends to operational records like shipping logs and customer data files. Under expressio unius, the argument would be that by specifying financial records and accounting systems, the parties deliberately excluded operational records from the audit right. If they had wanted operational records included, the argument goes, they would have said so.
Like all canons, expressio unius is not an ironclad rule; it is a presumption that can be overcome by contrary evidence of intent. Courts recognize that drafters sometimes omit things not because they meant to exclude them but simply because they did not think of them. The canon is more persuasive when the list at issue appears to be exhaustive by design — when it seems like the drafter was trying to specify everything covered — and less persuasive when the list appears to be illustrative.
For business owners, the lesson is that the structure of your lists matters. If you intend a list to be complete and exclusive, say so: ‘The following, and only the following…’ or ‘limited exclusively to…’ If you intend the list to be illustrative, use language like ‘including without limitation’ or ‘such as.’ These small drafting choices have significant interpretive consequences.
Noscitur a Sociis: Words Are Known by Their Associates
Noscitur a sociis means ‘a word is known by the company it keeps.’ This canon provides that the meaning of an ambiguous word or phrase is informed by the words and phrases surrounding it in the contract. When a term could have multiple meanings, courts look to the context in which it appears to determine which meaning is most consistent with the surrounding language.
This canon often operates in tension with ejusdem generis but at a different level of abstraction. Where ejusdem generis limits general terms by the specific items in a list, noscitur a sociis is more broadly about using contextual associations to resolve the ambiguity of a single term. If a contract uses the word ‘transfer’ in a section dealing with intellectual property assignments and licenses, a court applying noscitur a sociis would likely read ‘transfer’ to refer to IP rights transfers rather than, say, a transfer of employees or a wire transfer of funds.
Practically, this canon reinforces the importance of placing related provisions together and of using terminology consistently throughout a contract. If a word appears in multiple provisions with different surrounding context, its meaning may be different in each location — or a court may have difficulty determining its meaning anywhere in the document. Consistent, context-sensitive drafting reduces the risk that noscitur a sociis will produce an unintended result.
The Rule Against Surplusage: Every Word Should Mean Something
Courts interpreting contracts generally try to give meaning to every word, clause, and provision. Under the rule against surplusage (also sometimes called the rule against redundancy), an interpretation that renders a portion of the contract meaningless or superfluous is disfavored. Courts prefer readings that give independent effect to every part of the agreement.
This canon matters most in disputes where one party’s interpretation would make a provision redundant or would make certain language add nothing to what is already said elsewhere. If you argue that ‘best efforts’ means the same thing as ‘reasonable efforts’ in your contract, the rule against surplusage counsels against that argument — because if they meant the same thing, why would the drafter have used different language in different places? The use of distinct terms is presumed to signal distinct meanings.
For drafters, this canon is a reason to be deliberate about including every provision you actually want and removing provisions you don’t need. Boilerplate clauses that are copied from form agreements without review can create surplusage problems if they overlap with negotiated terms or with each other. The more tightly your contract is drafted, the less surplusage there is, and the cleaner the interpretive analysis.
The rule against surplusage also counsels against including provisions that are merely aspirational or hortatory without adding any legal content. If a provision says ‘the parties agree to cooperate in good faith,’ and your contract is governed by law that already implies a duty of good faith, the provision adds little. If you intend it to have specific substantive content beyond the implied duty, spell that content out explicitly — otherwise, the provision may not accomplish what you hoped.
Specific Controls Over General: How Courts Resolve Internal Conflicts
When two provisions of the same contract conflict, courts apply the principle that specific provisions control over general ones. A specific clause addressing a particular situation takes precedence over a general clause that might otherwise govern. This makes intuitive sense: the more specific provision is more likely to reflect careful, considered attention to the particular circumstances than a broad catch-all.
A common example arises in contracts that have a general limitation of liability clause and a specific indemnification clause. The general clause might limit damages to some capped amount. The specific indemnification clause might create broader liability for certain categories of loss. Courts applying the specific-over-general canon would typically hold that the specific indemnification obligation is not subject to the general cap, even if the general language would seem to cover it.
This canon creates important drafting implications. If you have a general clause that you intend to apply universally — without exception for any specific provision — you need to say that clearly. Language like ‘notwithstanding any other provision of this Agreement’ preceding a limitation of liability clause is specifically designed to override the specific-over-general canon and ensure the limitation applies across the board. Without such explicit override language, a specific provision may escape the general rule.
How to Use These Canons in Practice
Understanding the canons of construction serves two complementary purposes. First, when you are drafting or reviewing a contract, you can test your language against the canons to predict how a court might interpret it. Ask yourself: if this provision were disputed, which canon would apply, and would the result be what I intended? If the answer is no, revise before signing.
Second, when you are in a dispute, the canons provide a framework for constructing and evaluating legal arguments. If your preferred reading is consistent with multiple canons — ejusdem generis limits the general term, expressio unius excludes your opponent’s reading, and the specific-controls-over-general rule favors your position — you have a strong interpretive case. If the canons point in multiple directions, the dispute is more uncertain, and the value of settlement increases.
It is worth noting that courts treat the canons as useful guides, not binding rules. A canon can be overcome by clear contrary evidence of the parties’ intent, and different canons sometimes point in different directions. Courts have discretion in applying them, which means that in close cases, results can be unpredictable. The best approach is always to draft clearly enough that none of these canons need to be invoked at all — but when they do come into play, knowing the framework puts you in a much better position.