What Is a Definition?
A definition is a statement that explains the meaning of a word, phrase, or concept. At its most basic level, a definition answers the question "What does this word mean?" However, the nature of definitions is far more complex and nuanced than this simple description suggests.
The word "definition" comes from the Latin definitio, from definire, meaning "to set bounds to" or "to limit." This etymological origin is revealing: a definition literally sets the boundaries of a word's meaning, marking out what the word includes and what it excludes. A definition of "triangle" must include all triangles (three-sided polygons) and exclude all non-triangles (circles, squares, and everything else).
Understanding what a definition is—and what different types exist—is fundamental to using a dictionary effectively. Definitions are the core content of any dictionary, and knowing how they work helps you extract maximum value from every entry you read.
The Purpose of Definitions
Definitions serve several essential purposes in communication and learning:
Communicating Meaning
The primary purpose of a definition is to convey the meaning of a word to someone who does not already know it. When a child asks "What does 'enormous' mean?" and a parent answers "It means very, very big," the parent is providing a definition that transfers understanding of the word from one person to another.
Reducing Ambiguity
Many words have multiple meanings, and definitions help clarify which meaning is intended in a given context. The word "bank" could mean a financial institution, the edge of a river, or the act of tilting an aircraft. Definitions distinguish between these senses, reducing the potential for misunderstanding.
Standardizing Usage
In specialized fields—law, medicine, science, technology—definitions establish precise, shared meanings for technical terms. A legal definition of "negligence" or a medical definition of "hypertension" ensures that professionals within that field understand the term in exactly the same way.
Enabling Learning
Definitions are tools for learning. When you encounter an unfamiliar word while reading and look it up in a dictionary, the definition enables you to understand the text and adds a new word to your vocabulary. This process of definition-based learning is central to vocabulary building.
Types of Definitions
Not all definitions are created equal. Different contexts call for different types of definitions, each with its own characteristics and purposes.
Lexical Definitions
Lexical definitions are the type found in dictionaries. They report the established, conventional meaning of a word as it is used by speakers of the language. A lexical definition does not create or stipulate a meaning; it records how the word is actually used. When Merriam-Webster defines "cat" as "a small domesticated carnivorous mammal," it is reporting how English speakers use the word "cat."
Lexical definitions can be evaluated as accurate or inaccurate—they are meant to correspond to actual usage. If a dictionary defined "cat" as "a large herbivorous reptile," that would be an inaccurate lexical definition because it does not match how the word is used.
Stipulative Definitions
A stipulative definition assigns a specific meaning to a word for a particular purpose, regardless of how the word is ordinarily used. Scientists, philosophers, legal scholars, and technical writers frequently use stipulative definitions. For example, a researcher might write: "For the purposes of this study, 'adolescent' is defined as a person between the ages of 12 and 18."
Stipulative definitions cannot be "true" or "false" in the way lexical definitions can—they are proposals about how a term will be used in a specific context. They can, however, be useful or unhelpful, clear or confusing.
Precising Definitions
A precising definition takes a word that is already in use but vague, and makes it more precise for a particular purpose. Legal definitions often function this way. The everyday word "adult" has a general meaning, but for legal purposes, it might be precisely defined as "a person who has reached the age of 18 years."
Persuasive Definitions
Persuasive definitions attempt to influence attitudes by framing a word's meaning in emotionally loaded terms. Defining "taxation" as "legalized theft" or "freedom" as "the right to live without government interference" are persuasive definitions that embed a particular viewpoint in what appears to be a neutral statement of meaning. Recognizing persuasive definitions is an important critical thinking skill.
Ostensive Definitions
An ostensive definition explains a word's meaning by pointing to or showing examples. If someone asks "What does 'red' mean?" and you point to a fire truck, a stop sign, and a ripe tomato, you are defining "red" ostensively. This is often how young children learn their first words—by seeing objects paired with their names.
Extensional Definitions
An extensional definition specifies the meaning of a word by listing all the things it applies to. "The Great Lakes are Lake Superior, Lake Michigan, Lake Huron, Lake Erie, and Lake Ontario" is an extensional definition—it defines the term by listing all its members.
Intensional Definitions
An intensional definition specifies the meaning of a word by describing the properties that something must have to be covered by the term. "A triangle is a polygon with exactly three sides" is an intensional definition—it describes the essential properties rather than listing all triangles.
How Dictionaries Create Definitions
The process of creating dictionary definitions—known as lexicography—is a specialized craft that combines linguistic analysis, editorial judgment, and evidence-based methodology. Understanding this process helps you appreciate why dictionary definitions are reliable and how to interpret them correctly.
Corpus Analysis
Modern dictionaries base their definitions on evidence from language corpora—vast databases containing billions of words of real-world text from books, newspapers, websites, and transcribed speech. Lexicographers analyze how words are used across thousands of contexts to determine their range of meanings.
The Defining Process
Lexicographers follow established conventions when writing definitions. The most common approach is the analytical definition, which identifies the word's genus (the broader category it belongs to) and differentia (the features that distinguish it from other members of that category). For example:
hammer — a tool [genus] used for driving nails, consisting of a heavy head attached to a handle [differentia]
This genus-differentia structure ensures that definitions are both precise enough to identify what the word means and broad enough to cover all its applications. The craft of creating clear, accurate definitions is what separates professional lexicography from casual paraphrasing.
Defining Vocabulary
Learner's dictionaries use a controlled defining vocabulary—typically 2,000–3,000 common words—to write all their definitions. This ensures that language learners can understand definitions without needing to look up the words used in the definition itself. Standard dictionaries for native speakers do not impose this restriction, allowing for more nuanced and precise definitions.
What Makes a Good Definition?
Not all definitions are equally effective. A good definition possesses several key qualities:
Accuracy
A definition must correctly describe the word's meaning. It should cover all legitimate uses of the word (not too narrow) without including things the word does not apply to (not too broad). Defining "bird" as "a flying animal" is too broad (bats fly but are not birds) and too narrow (penguins and ostriches are birds but do not fly).
Clarity
A definition should be understandable to its intended audience. Defining an everyday word using obscure technical language defeats the purpose. The definition should be clearer than the word itself—a circular definition like "a runner is someone who runs" provides no real information.
Conciseness
Good definitions are as brief as possible while remaining accurate and complete. Wordiness obscures meaning. A definition should contain exactly the information needed to distinguish the defined word from all other words—no more, no less.
Non-circularity
A definition should not use the word being defined (or a close derivative) in the definition itself. "Happiness is the state of being happy" is circular and unhelpful. This challenge is one reason why defining abstract concepts like emotions can be so difficult.
Appropriate Register
The language of the definition should match the dictionary's audience. A children's dictionary definition of "democracy" will use simpler language than an academic dictionary's definition of the same word.
Challenges of Defining Words
Defining words is far more challenging than most people realize. Several persistent difficulties confront lexicographers.
Abstract Concepts
Abstract words—love, justice, beauty, truth, freedom—are notoriously difficult to define because they refer to concepts that cannot be pointed to or measured directly. Different people may understand these words somewhat differently, and any definition risks being either too vague to be useful or too specific to capture the word's full range of use.
Basic Words
Paradoxically, the most common and basic words are often the hardest to define. Try defining "the," "is," "do," or "thing" precisely. These words are so fundamental that there are few simpler words available to explain them. The word "set" in the Oxford English Dictionary has one of the longest entries in the dictionary, with dozens of distinct senses.
Cultural and Context-Dependent Meaning
Some words carry meanings that depend heavily on cultural context, social situation, or shared knowledge. Idioms like "break a leg" (meaning "good luck") cannot be defined by combining the definitions of the individual words. Slang often carries social meaning that is difficult to capture in a formal definition.
Evolving Meaning
Word meanings change over time, and definitions must keep pace. The word "literally" has developed a figurative intensifier sense ("I literally died laughing") alongside its traditional sense. The word "nice" has shifted meaning dramatically over centuries, from "ignorant" to "pleasant." Dictionaries must decide when and how to reflect these shifts in their definitions—a challenge discussed in our article on new words in English.
Multiple Senses and Polysemy
Most words in English have multiple senses—a phenomenon linguists call polysemy. The word "run," for instance, has over 600 senses in the Oxford English Dictionary. A dictionary must identify and define each distinct sense while organizing them in a logical way.
Dictionaries handle multiple senses in different ways:
- Frequency ordering: The most common sense is listed first, with less common senses following. This approach helps readers find the most likely meaning quickly.
- Historical ordering: Senses are listed from oldest to newest, tracing how the word's meaning has developed over time. The OED uses this approach.
- Logical ordering: The core or central sense is listed first, with derived and figurative senses following in a logically connected sequence.
Understanding how your preferred dictionary orders senses helps you navigate entries more efficiently. This is a key part of knowing how to use a dictionary well.
Definitions in Philosophy and Logic
The nature of definitions has been a subject of philosophical inquiry since ancient Greece. Plato's dialogues often revolve around attempts to define abstract concepts—justice, knowledge, beauty, courage. Aristotle formalized the genus-differentia approach to definition that dictionaries still use today.
In logic and mathematics, definitions are formal statements that establish precise meanings for terms within a system. Unlike dictionary definitions, which describe usage, mathematical definitions are stipulative and exact—they create the meaning rather than reporting it. "A prime number is a natural number greater than 1 that has no positive divisors other than 1 and itself" leaves no ambiguity.
The philosopher Ludwig Wittgenstein challenged the classical view that all instances of a concept share common features that a definition can capture. He proposed instead that many concepts—like "game"—are held together by "family resemblances," overlapping similarities without any single feature shared by all members. This insight has influenced how modern lexicographers approach the definition of complex, multifaceted words.
How to Read Dictionary Definitions
Reading dictionary definitions effectively is a skill that improves with practice. Here are strategies for getting the most from the definitions you encounter.
- Identify the part of speech. Know whether the word is being defined as a noun, verb, adjective, or other part of speech, as this determines which definition applies to your context.
- Read all senses. Do not stop at the first definition. Scan all numbered senses to find the one that fits your context.
- Study the examples. Example sentences show the word in use and can clarify nuances that the definition alone may not convey.
- Note usage labels. Labels like "informal," "technical," or "archaic" tell you important information about when and where the word is appropriate.
- Follow cross-references. If the definition refers you to another entry, follow the reference. These connections build a more complete understanding.
- Compare across dictionaries. Different dictionaries define the same word differently. Consulting multiple sources gives you a richer understanding of the word's meaning.
Conclusion
Understanding what a definition is—and the many forms definitions can take—enriches your relationship with language. Definitions are not just dry explanations in dictionaries; they are fundamental tools of human communication, learning, and thought. Whether you are looking up an unfamiliar word, writing a technical document, or debating the meaning of an abstract concept, definitions are at the heart of the endeavor.
The art and science of crafting good definitions has been refined over the centuries-long history of dictionaries. Modern dictionaries, drawing on vast corpora and the collective expertise of skilled lexicographers, provide definitions that are more accurate, comprehensive, and accessible than ever before. Learning to read and use these definitions effectively is one of the most rewarding skills any language user can develop.