I don’t understand definitions.

Let’s take this question: “What is a woman?”

Now if I am a Platonic Idealist (or some other essentialist) then I think that all women share the same essence and will attempt to give a comprehensive (as opposed to extensive) definition of “woman” according to its nature. I realize that not all instances of the “woman” class will be accurately described by its essential properties (a.k.a “proper accidents” as opposed to non-essential a.k.a “accidental” properties), but the nature of the concept “woman” will be adequate.

If I am a nominalist, then I reject the concept of natures or essences in so far as they actually objectively exist, so I can only define “woman” extensively (by including and describing every instance of the “woman” class).

The problem in the first case is that the definition might not describe all instances of the subject - is this a bad definition or is it just a case of every rule having an exception?

The problem in the second case is that the definition seems to be very loose and opposite to objective material reality.

How are we supposed to define anything?

When people define woman as “humans who can give birth”, it is met with the response “not all woman are capable of giving birth, so you must think they aren’t women!” Does this mean that the definition is bad or does it mean that there are implications in the word “woman” (like “healthy” woman, or “humans who, 'if healthy’, can give birth” implying that a normal, healthy woman is capable of giving birth and that a woman incapable of giving birth is not healthy)? Commonsensically, a woman who can’t give birth is still a woman, so is “giving birth” an accidental property of "woman" as opposed to an essential one? It seems like if you give any property, even if it seems essential, there are instances where what we normally call “woman” doesn’t exhibit this essential property which either means the property is non-essential (and thus a bad definition) or we are dealing with an exception to the rule...

Am I making myself clear? How do we know that we define something properly when any exception could either mean that the definition itself is bad and needs to be changed to fit better data or the exception to the definition is inconsequential because of some implicit understanding in the word/definition itself?

  • 7
    It is a lot easier to define men: they aren't women.
    – Scott Rowe
    Commented Jul 27, 2023 at 2:25
  • 2
    Where's the possibility that definitions are an ongoing process? en.wikipedia.org/wiki/Meno "Meno, unable to adequately define virtue, is reduced to confusion or aporia.[2] Socrates suggests that they seek an adequate definition for virtue together..." (why do I even bother...this site has gotten in a tizzy recently)
    – J Kusin
    Commented Jul 27, 2023 at 2:26
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    @gs Well what about this question, which hits on the same point: "How many arms do people have?" On one hand, a general (essential) answer would be : "people have two arms". The response would be: "but that is not rigorous enough because that would discount humans without two arms as people". So again, either the definition is in fact too narrow, or "having two arms" is accidental. Commented Jul 27, 2023 at 2:47
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    @ProfessorFinesse type-which-corresponds-to serves us well again. Humans are that species of animals which has, among its characteristics, a near-universal propensity towards having two arms. Modern people have access to the concept of the genotype, but it's unnecessary; ancients were more than capable of defining humans distinctly from armchairs and including injured humans and armchairs in their proper categories.
    – g s
    Commented Jul 27, 2023 at 4:22
  • 2
    @user253751 How do you plan to ask A question? I thought words needed to point to specific examples. What is this a question you speak of? I know about this question and that question, but a question is a mystery to me, please explain it. (A non-serious inquiry to express my meaning.)
    – g s
    Commented Jul 28, 2023 at 16:11

7 Answers 7


Do not expect to find a perfect definition.

A definition is an expression of the meaning of something (the problem of the thing, what is a thing, is another), and meanings are intended normally for communication. The content of the definition is defined by the goal of the communication. Depending on the goal, the definition might approach different dimensions of the thing.

For example, you feel pain, and you need to communicate about it. If you are a baby, a perfect definition of pain is "ouch!". If you are an MD, "a subjective conscious mental perception of a feeling often caused by intense or damaging stimuli" would be fine. If you are a common mortal, "an unpleasant sensory and emotional experience" is ok. From a bio-physiologist perspective, pain could be a warning mechanism; from a religious perspective, pain might be a source of purification of the soul.

How do we know that we define something properly

You know the definition is proper if the meaning has been communicated by means of the definition, in the intended dimensions, to the target public, so that both of you can interact using such meaning.

Of course, this requires trial and error, but there's a lot of previous definitions you can use to start from, for example, those in the dictionary.


Several options to define a word.

1. Explicitly define a word in any arbitrary way you want

and then use it according to your definition. This method often works for new terms that you invented, such as some terms in mathematics.

It can be problematic if you try to explicitly redefine a common word. Common words already have common definitions. People may refuse to accept your definition, or insist you just use a different word.

If you use this method, you can't (or logically shouldn't) rely on connotations and associations of the word outside your own definition of it. If I explicitly define "a chair" to be "a four-legged wooden table, painted blue," then I can no longer assume that people sit in "chairs," and any conclusions I reach about my "chairs" are not applicable to chairs in common usage of the term.

If you arbitrarily define a word, there's no normative component, where you get to say that other people ought to use the word the same way you have.

2. Rely on common usage

This is the method the dictionary uses, and you can use it too. You just specify which common-usage sense you want to use (there may be several) and then use the word. It may not even be necessary to specify which sense you want to use; it may be obvious from context. Take care, however, because conclusions you make about one common-usage sense of the word do not apply to any other sense of the word. To forget this is to commit the fallacy of equivocation.

3. Attempt to clarify a common-usage definition, and fix problems/inconsistencies/ambiguities.

This method is used often in philosophy. What is "knowledge"? What is "consciousness"? What is "good"? What does it mean to be "at fault"? What is a person's "identity"?

To make a good definition of this sort involves the following kinds of activities:

  • Identify problems and ambiguities in the common-usage definition
  • Attempt to break the common-usage definition into clearly definable parts
  • Propose your own definition in terms of these clearly-definable parts
  • See if you can devise thought experiments where your own definition would strongly contradict common usage (e.g. Gettier problems)
  • See if your own definition can be brought into contradiction with itself
  • See if your definition is ambiguous in certain situations
  • If there is contradiction or ambiguity, try to revise your definition

In the end, if you have sufficiently strong agreement between your definition and common usage, and if your definition is sufficiently clear and internally consistent, you might propose that your definition is the "true" nature of the common term, and claim that other people ought to use it.

The persuasive appeal of this would be that your definition helps people to think clearly about the term, when the term was unclear before, and that the term otherwise functions mostly the same as the previous term. Adopting your definition, you might argue, helps people to think more clearly in general.

We could use the metaphor of removing a rusty gear from a machine, and then machining a new gear that is a drop-in replacement for the rusty one except without some of the defects. Your new gear meshes more smoothly with other gears already in the machine. Having done this, you have some basis to claim that an engineer maintaining such machines "ought to" use your type of gear in place of the rusty one.

Of course, others remain free to disagree.

  • 4
    I wish someone would define "Scotsman" once and for all.
    – Scott Rowe
    Commented Jul 27, 2023 at 2:28
  • 2
    @ScottRowe the only true scotsman is (was) Sean Connery
    – armand
    Commented Jul 27, 2023 at 5:06
  • @armand, Yesh, Seah Connery wash a true Scotshman.
    – Hudjefa
    Commented Jul 27, 2023 at 9:24
  • Method 1 is very common in mathematics for old terms that you didn't invent, so you can draw exact conclusions about what you defined. If I can draw precise conclusions about four-legged wooden tables, painted blue, I've made a solid contribution to chair science even if somebody else still has to figure out the red ones, the ones with three legs, and determine which ones are meant for sitting. Commented Jul 28, 2023 at 17:29
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    if you ever wondered about mathematical terms like constructible numbers and safe primes, they came from papers like "Which numbers can we construct using ruler and straightedge?" and "Which prime numbers are the best to use in secret codes?" where the author quite sensibly called the ones he could construct "constructible numbers" and then the name somehow escaped the context of the paper. Commented Jul 28, 2023 at 17:31

Excellent question.

Definitions are a little more complicated than you present them. Robinson in his Definitions covers two major categories of definitions: one is the real definition, which he believes shouldn't be a definition at all; the other is a lexical definition which is a linguistic artifact that is part of any language-game. The first might be better understood as an attempt to articulate a concept, and the latter is might be better understood as an attempt of people to use language correctly. The latter notion of definition is easy, because it is merely achieved by the consensus by people about words that serve a particular purpose. For instance, a precising definition in physics will merely articulate words in such a way to avoid ambiguity and prevent or encourage action. Physicists do this by including math and measurement in their definitions so that if someone else is in doubt, they can use numbers to settle the ambiguity or vagueness. This is particularly important in operational definitions, where what is being defined doesn't physically exist.

Of more interest to this question is Robinson's notion of a real definition. It is what is commonly recognized as a discussion of what is real and existent. Obviously, then, the definition is an ontological tool and helps us to perceive and discuss reality, and is an aspect of what Quine calls semantic ascent. From WP:

[Semantic ascent] is the shift from the material mode of language to the formal one. In the formal mode of language we are at a different level. Rather than talking about miles as objects we are talking about what this word 'mile' even means, what it refers to and if it even refers at all. In the formal mode, people with different conceptual schemes might be able to have a reasonable discussion because they are talking about something their conceptual schemes have in common: language.

Thus, we have language, which represents reality, and we have the physical universe which is often considered the foundation of reality. A real definition is means by which come to agreement about reality, which is no easy task, but when successful establishes a type of intersubjective agreement. Educated people in 12th century Rome had one view of reality, and their counterparts in 21st century Chicago have a different view. In fact, the role of definition in this sense is largely about preserving a worldview.

Now, how do we settle on definitions? First, not all people agree on all definitions, either in formulation or method. Language communities agree, but there are many different language communities in the world. How Hitchens, Dawkins, Harris, and Dennett define God, for instance, greatly differs from how the Pope and his Cardinals do. How are we to know who is "right" and who is "wrong"? Perhaps the answer lies in the question 'Do the terms right and wrong or true and false apply to worldviews at all?' Perhaps pragmatic standards such as adequacy and inadequacy are better descriptors.

Whatever your views on the generalization of truth conditions, know that there are three common ways people define things:

  1. The genus-differential definition - how things are the same; how they differ.
  2. Definition by sufficiency and necessity - what characteristics are required and/or optional
  3. Prototypical definitions - how many and of what sort of characteristics does something have

To explain each would be to go beyond the scope of this question. Suffice it to say, that if you master each of these techniques, you'll have a better notion of which strategy is the best strategy in a given context. I say that because definitions are motivated by needs and in different situations. Now we can answer your question:

How do we know that we define something properly when any exception could either mean that the definition itself is bad and needs to be changed to fit better data or the exception to the definition is inconsequential because of some implicit understanding in the word/definition itself?

"Properly" depends on the context, so there is no one right answer. Prototype theory, however, handles just the case you invoke, a case with exceptions or contradictions of extension. This stems from Wittgenstein's reflection on family resemblance. From WP's article on prototype theory:

In this prototype theory, any given concept in any given language has a real world example that best represents this concept. For example: when asked to give an example of the concept furniture, a couch is more frequently cited than, say, a wardrobe. Prototype theory has also been applied in linguistics, as part of the mapping from phonological structure to semantics.

So, if there are exceptions to the rule, or if there is a deviation from the best example, that's fine, because membership to the category is continuous, not discrete. That is, one needn't say a definition is true or false of an object, but that there's a degree of belonging. In other words, rather than expecting a definition to work as a yes-it-is or no-it-isn't, you can also use definitions to say, it is somewhat.

There's a lot to the nuance of definition, and it's not possible to cover the objections and the responses here, but suffice it to say, if you get Robinson's book and give a read, you'll be better off than before. The art of definition is not simple.

  • This has been the best answer by far. I learned about the first kind of definition along with the extension and comprehension (intention) of terms from Peter Kreeft's Socratic Logic but after thinking really hard about it and trying to apply it to stuff, it left me with lots of questions and holes. I've heard of "language games" when people are about Wittgenstein but I don't know much about him. I will definitely check out Robinson's Definitions . (1/2) Commented Jul 29, 2023 at 2:20
  • From what you describe, his "real definitions" seems to be what Kreeft talks about since he (like the ancient Greeks) comes from a metaphysical realist POV. Thank you for your insight. Commented Jul 29, 2023 at 2:21
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    Yeah, no worries. I have a profound interest in definitions, and if you manage to read Robinson's book, and have questions, or a recommendation next in the list, let me know. The way I see it, there's an arc of sophistication in the term 'reality' that goes from direct realism to anti-realist position like mereological nihilism back to conceptualism.
    – J D
    Commented Jul 29, 2023 at 15:38
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    Regarding worldviews, Nonduality would say that because they are made up, they can't be right or wrong. I could think: "it is too hot to go outside", yet see dozens of people walking around out there. I can't be right or wrong, only have a preference. We prefer reality to be some way, but, you know, too bad! Ha ha
    – Scott Rowe
    Commented Jul 30, 2023 at 14:07
  • 1
    @ScottRowe Absolutely, buddy.
    – J D
    Commented Jul 30, 2023 at 15:40

How do we define things?

We don't. We define words, the words we use to talk about things. To define a word is to specify what thing we use the word to refer to.

We don't define things, but we identify them. We point a finger and say "This is the Moon". This effectively identifies what we call "the Moon" and at the same time what we mean by the word "Moon", and so it is a definition of the word "Moon".

Consequently, we don't define what a woman is. A woman is what it is and she doesn't need your definition to be what she is. Instead, we define the word "woman".

How we define the word "woman" is then a matter for each of us. Our definition should express what we mean when we use the word "woman". However, if we want to speak, say, English, we may choose to use the definition provided by professional lexicographers, in what we call "dictionaries".

In the case of the word "woman", the definition may go like this:

An adult female human.

The clear benefit of using dictionaries is that they usually provide definitions in line with how the word is actually used by most speakers of the language, so that we can be pretty confident that we will be understood.

Sometimes, a definition may not be satisfactory, which can be more often the case with politically sensitive words and technical terms, but it is nonetheless more often the case that the definition will be perfectly understandable, as is the case with "An adult female human".

How do we know that we define something properly when any exception could either mean that the definition itself is bad and needs to be changed to fit better data or the exception to the definition is inconsequential because of some implicit understanding in the word/definition itself?

Definitions are by nature a work in progress. What we thought a woman was 2,000 years ago was probably different from what we think today. The thing didn't change, but our understanding of the thing did, and this is reflected in how we define the word "woman". Thus, definitions are not supposed to be cast in iron or somehow absolutely true for now and ever. Instead, each new edition of a dictionary will amend this or that definition to reflect our current understanding of the world. The dictionnaire de l'Académie Française is now in its 9th edition, while the first was in 1694, and it is usually interesting to go through the changes from one edition to the next.

When people define woman as “humans who can give birth”, it is met with the response “not all woman are capable of giving birth, so you must think they aren’t women!”

Yes, and it is trivially true that not all women can give birth, which just means that the definition “humans who can give birth” is clearly wrong.

This is also why it is a good idea to at least start from dictionaries. You can always try to improve on the definition provided by a dictionary, and this allows you to take advantage of the expertise of the professionals in this matter.

This also means that definitions are mostly determined by the prevailing usage in a given community of speech, but there is clearly never such a thing as "the only correct definition" of a word. Definitions are in constant flux, much like life itself, which is probably therefore for the better. It is then up to you to decide which definition you are going to use, and then face the consequences of your choice.

  • If it's clearly wrong to use "humans who give birth" when it applies to the general case (generally, women can give birth), what would be a better definition that accounts for all cases? This is the crux of my problem. Either the definition works for the general case, but is not perfectly accurate or it seeks to include all aspects of the subject by being overly reductive. Where are the limits of each? (1/2) Commented Jul 29, 2023 at 2:13
  • Is the phrase "Earth has gravitational force" accurate because it covers the general case or is it inaccurate because it does not account for those instances where there is no gravity on Earth (like a man-made vacuum)? Is it reasonable to define humans as the classic Aristotelian "rational animal" or is it too narrow because there are humans who suffer from mental retardation? What exactly is the difference between a cup and a bowl? If "cup" is defined by its size relative to a bowl, it includes most cups but excludes bowl-sized cups. Etc etc. (2/2) Commented Jul 29, 2023 at 2:13
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    @ProfessorFinesse "what would be a better definition that accounts for all cases?" The ones given dictionaries seem all good to me. 2 "Either the definition works for the general case, but is not perfectly accurate or it seeks to include all aspects of the subject by being overly reductive." An adult female human is perfectly general and accurate. It is always the case that a woman is an adult female human and that an adult female human is a woman. Commented Jul 29, 2023 at 9:38
  • @ProfessorFinesse there is no contradiction between saying that the Earth has gravitational force and saying that there are locations in the Earth where there is no gravity. - 2. "Is it reasonable to define humans as the classic Aristotelian "rational animal"" Aristotle's definition is that man is a rational animal, where man means the species, not any particular individual. Aristotle presumably knew that some humans are mad and therefore not necessarily rational. Commented Jul 29, 2023 at 9:46
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    So if someone wonders what a woman is, we throw the book (dictionary) at them.
    – Scott Rowe
    Commented Jul 30, 2023 at 14:20

The Oxford Advanced Learner's Dictionary defines "definition" as:

an explanation of the meaning of a word or phrase, especially in a dictionary

The Stanford Encyclopedia of Philosophy uses a great many words to talk about the term "definition"; but the 6 or so categories of different definitions all have in common that a definition defines a "term" (i.e., a word, a phrase).

Considering how many philosophers of the highest calibre have wrestled with defining concepts like "object", "concept", "reality" and so on and forth, I think we can safely say you will not find a more useful definition than that. To put it bluntly: a definition says what a word means, it has nothing to do with reality.

In other words: anything which explains the meaning of a word or phras is a definition. The concept of "definition" does not need more or less.

Importantly: we do not define physical objects, we do not define reality; we do not define anything except words, phrases, terms. The latter are always just abstractions from reality. It is completely normal that a given word may or may not apply to physical instances depending on whom you are talking with. It is completely normal that different people work with different definitions. We see this all day when following political discussions, or social media threads, or even just when talking with friends and family.

So a concrete, individual person you are seeing in front of you is simply not something that the concept of "definition" applies to. A definition always applies to words, phrases, terms, and explains what we mean by those.

The form a definition takes is itself not really defined. You can look up a term in a dictionary and get a formal definition (which might or might not be true or generally accepted or even understood). You can also have an implicit definition somewhere in your brain (which would make up your conscious or unconscious world-view). Definitions can be vague or specific, and will still be definitions. You can define terms by example, by comparison, by some kind of rules or metric, by stipulating a new meaning, and so on and forth. You can, in general, easily have circular definitions (hopefully not if you work in an exact science).

I don’t understand definitions.

So in short, there is nothing to be confused about. There is nothing to understand, really. A definition is simply anything that explains what a word means, in any form you could imagine. They can be as varied as people; as vague as all language.

The word you picked, "woman", is probably one of the most hotly discussed terms you could have picked (together with "man" and all the other gender-related terms). It is no wonder that you can find no common, easy to understand definition. Many people will have different definitions of these words, which is the reason why the communication is often fraught and futile. Especially since in this particular case, the people who do the thinking and talking are sometimes heavily influenced by whatever outcome such a discussion would have - so aside from cold, logical, definitions, there a massive amounts of other interests in the issue. It is a good example to show how it is futile to ask for a definitive, final definition for a term.

  • The more things change, the more words stay the same. I still say that defining 'man' is easier, and women are simply not men (but still human and all that). Why don't people do things the easy way, like my 6th grade math teacher said? She was not a man, maybe we should listen to her?
    – Scott Rowe
    Commented Aug 1, 2023 at 10:34
  • If your original question is mainly about the words "man" and "woman" (and didn't only use them as examples) then you should probably open a separate question. If the comment was a joke, then you probably know the answer already. ;) @ScottRowe
    – AnoE
    Commented Aug 1, 2023 at 11:36

There are, it seems, minimally, 2 ways to define anything:

  1. Objectively. This method would require the existence of a class (the members being tokens and the class itself being the type). That would mean if I say Smith is a man then the class of men should exist, to which Smith belongs. This type of definition is not arbitrary as reality constrains the definition - definition has to match some aspect of reality. An example would be the word "man", its definition is abstracted from token men. Reality decides, she calls the shots.

  2. Subjectively. You're completely free, sky's the limit. While a class seems necessary, that class can be empty. An example would be the word "unicorn". Notice that a unicorn is not abstracted from token unicorns. We decide, we run the show.

  • 1
    Various errors. There's no "objective" hierarchy of classes, the dictionary is a circular set of references. In addition, not all definitions are classes, even in science, other methods of definitions exist (e.g. synonyms, etymology (definition by etymological composition), non-positivist (definition by negatives), etc.). In addition, objectivist existence implies an absolute truth, independent of minds, which is an abandoned approach for long in most modern branches of philosophy).
    – RodolfoAP
    Commented Jul 27, 2023 at 10:20
  • I see. Thanks fer the update. I was responding to the OP's self-admitted confusion. What's there ta be confused about definitions? That's from where you stand, a locus I don't enjoy, but am aware of. And of course a question that's too obvious ta ask.
    – Hudjefa
    Commented Jul 27, 2023 at 10:32
  • 1
    I don't think you understand. Is the phrase "Earth has gravitational force" accurate because it covers the general case or is it inaccurate because it does not account for those instances where there is no gravity on Earth (like a man-made vacuum)? Is it reasonable to define humans as the classic Aristotelian "rational animal" or is it too narrow because there are humans who suffer from mental retardation? What exactly is the difference between a cup and a bowl? If "cup" is defined by its size relative to a bowl, it includes most cups but excludes bowl-sized cups. Commented Jul 29, 2023 at 2:15
  • 1
    @ProfessorFinesse, good point. 🍜☕
    – Hudjefa
    Commented Jul 29, 2023 at 2:38
  1. We describe the thing we want to define, list all the essential properties that distinguish it from other things.

  2. Then we give that thing a name.

Definitions enable us to discuss complex concepts without spelling out their descriptions in every sentence.

  • 1
    In the OP question, I think it founders on deciding the "essential properties".
    – Scott Rowe
    Commented Jul 27, 2023 at 10:56
  • 1
    What are the essential properties of a screwdriver
    – J Kusin
    Commented Jul 27, 2023 at 22:53
  • @JKusin it drives screws? 'woman' is a bit harder, what the heck do they do?
    – Scott Rowe
    Commented Jul 27, 2023 at 23:50
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    @JKusin if you are using a screwdriver to do something other than drive screws, then it has no essential properties qua a screwdriver. It's just a lump of atoms at that point. Definitions are for use, of things as they are used, not just random labels. "It's all fun and games until someone gets hurt"
    – Scott Rowe
    Commented Jul 28, 2023 at 1:52
  • 1
    @JKusin I guess the difference would be between creating something to perform a function, like a screwdriver, with a name for your intention, and slapping a name on something after the fact. Anything could be a "murder weapon" - after it was used to kill someone. Otherwise we might just as well replace all nouns with murder weapon and get it over with. The mitochondria inside animal cells used to be free-living organisms, apparently. We don't know what they were called before the transition because there were no animals.
    – Scott Rowe
    Commented Jul 30, 2023 at 13:57

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