How to Write an Extended Definition
The first consideration is that a word doesn’t have one “right” meaning. There are more ideas or concepts than there are words, so the same word has to mean different things at different times. Conversely, different words or phrases can be used to name the same concept. What is necessary for clear thinking is that the parties to the conversation know what concept they are dealing with at any time. Therefore, in writing an extended definition, don’t define the word—rather explain the concept, and show why it’s important that the reader have clearly in mind the same concept you have in mind.
So a definition is partly fact (“This is what this word means when military historians, or beekeepers, use it.”) and partly reasoned opinion ("Let's agree, for now, to use this word in this way so we can understand each other and cometo areement on other things."
An extended definition can be built outward from a logical definition, also known as a dictionary definition, or a notional definition, or an Aristotelian definition. It takes this form:
Definiendum = genus + differentia.
The is the term or concept you are defining. The is the category or class which the definiendum is a part of. The is the characteristic or group of characteristics that set the definiendum apart from other members of the genus. For example, a choke cherry (definiendum) is a kind of cherry (genus) distinguished by its bitter, astringent taste that makes it inedible until it is cooked (differentia).
Even if you don’t state your logical definition in precisely this way in your essay, you should still have it clearly in mind. This is so your concept doesn’t shift to something else without your noticing it (this can happen easily), and so your reader will be able to reconstruct the logical definition from what you do say. Unless you’re sure of your step, it’s safest and most considerate of your reader to state the logical definition outright, usually near the beginning of your essay.
There are a few cautions to observe in putting together your logical definition. Don’t create a circular definition—don’t, that is, define a word in terms of itself, as in “Patriotism is the quality of being a patriot.” And definition by metaphor is not a logical definition, though it can have its uses: “Patriotism is the last refuge of a scoundrel” can convey something true, but it does’nt do the work of a definition, which is to tell us what patriotism is.
In an , the logical definition is elaborated on by various means, all of which are used to make the concept clearer in the reader’s mind. It’s up to you to determine which ones you use, and in what order, taking into account what it is you are defining, what you think your readers know already, whether you think they are simply unfamiliar with the concept, or have got it mixed up with other, somewhat similar concepts, and whether they are already disposed to see things as you see them, or will need convincing.
- Make sure you are clear about the use or the purpose of the definition. Why is it important for your reader to share your idea? Share the reason with your reader!
- Since the differentia is usually the part of the logical definition that needs the most clarification, develop it by comparison and contrast, and develop the contrasts by examples. Sometimes you need many examples; more often you can do better with one or two well-chosen examples if you accompany them with explanations why one example belongs inside the concept you are defining, and another on the outside. If you are defining domestic cat, for instance, you could show why a Maine Coon Cat is a domestic cat, while a Cerval Cat is not, though they are both small members of the cat family). If a suitable real example is not available, you can make up a hypothetical example, a useful fiction, so long as you are clear it is a fiction (you do not want people to think you really had a five-hundred-pound cat that slept on your bed and purred!).
- Show, by the same techniques, how your concept is different from other concepts that might, for whatever reason, be confused with it—for instance, why a skunk, though small, fluffy, and sometimes adopted as a pet, is not a domestic cat, or why using a polite conventional phrase like “fine” when you’re asked how you are, even if you have appendicitis, is not the same kind of thing as a white lie.
- Look for a test that can be used to determine whether something falls within the concept—an operational definition. If so, tell how it works, and why it was chosen. For example,a car qualifies as a Zero Emission Vehicle if it performs a certain way on a particular test. Operational definitions are used all the time in the sciences.
- Make the concept clearer by listing and describing its parts, or its subtypes, or its phases of development.
- Place the concept in relation to other concepts. Often cause-and-effect reasoning is useful here. Where does the domestic cat come from? Did the domestic cat become what it is because of the way people have treated cats over the centuries? How does your concept of domestic cat relate to the concept of pet? How is the concept of lying related to the concept of honesty—would you say a person is honest only if he never, ever lies?
- Especially if it helps make what you say under #3 or #6 clearer, you could give the history of the word you are using to name the concept you are defining. If your choice of that word is controversial, explain why you chose it.
- If value is part of the concept, deal explicitly with why that is so. Consider one commonly encountered example: for many people, something does not qualify as art unless it is of high quality—in their concept of art, there can be no bad art, because anything that’s bad isn’t art at all. That opens up new issues: What kind of goodness is needed to qualify? How would you determine what is good enough? People commonly talk and write sometimes as if value were part of the definition of an idea, while at other times they seem to assume that value is not a necessary part of the concept. When you are defining, commit yourself to one or the other.
The methods of development you choose will depend on your reason for defining the term as well as on your reader(s). There is no one right way. Usually a combination of methods is best. In any case, you must be clear in your own mind about why you want your readers to understand the concept you are defining; otherwise you cannot be clear to them, and they may never be motivated to understand you.
So pick a concept to define that matters to you.
You may want to look at a similar page at Rensselaer Polytechnic Institute which might be just different enough.