Intelligent people often like to use intelligent sounding words. Words like “nonplused”, “loquacious” and “limerance” spice up writing and conversation, add beauty to language, and can seem to give the speaker an aura of sophistication. Even those who don’t consciously cultivate having a large vocabulary may start to use such words automatically, having read them sufficiently many times in books or articles. Unfortunately, obscure words have a tendency to interfere with communication.
Sometimes it is argued that using obscure words is good because they allow us to more concisely express precise connotations than we otherwise could. Instead of saying “There were many hats in the barn” we can say “There was a plethora of hats in the barn.” The latter phrase means more than that there were just a lot of hats.
The issue though, is that most people don’t know the precise connotations of obscure words, and the word “plethora” serves as a good example. It is often defined to mean not just “a lot”, but an excess or overabundance. However, when you see the word used in context, while the implication of “many” is often clear, the specific connotations can be much less so. If you’ve never looked it up, but have just tried to understand the word from seeing its usage, it can be quite hard to pickup on this nuance. And if you do take the time to look it up, it can be easier to retain the gist than its subtleties, so one may forget the part about “excess” and remember only “a lot”. Since, by definition, obscure words don’t occur very often, we likely have not seen them used a great many times. That means that compared to common words, we don’t have many data points from which to infer precise meanings. Even if according to the dictionary “plethora” carries just the message you hope to express, that matters little if the people you are communicating with don’t understand your precise meaning.
Even those who know that the word “plethora” often has a connotation of excess may be doing little more than translating “plethora” to “excess” in their minds. That is, they might not have seen the word used enough times for “a plethora of pineapples” to mean something beyond “an excess of pineapples”. When this is true, little is gained by using “plethora” instead of just “excess.” The former is certainly less likely to be understood than the latter. And though it is true that the former sounds more sophisticated to some people and can act as a signal of education level, this can backfire at times. Some audiences will view the use of this word as pretentious, and according to one study at least, “Consequences of erudite vernacular utilized irrespective of necessity”, writing using complex vocabulary may even cause you to be viewed as less intelligent in certain contexts.
If you are writing poetry or fiction, where the beauty of the language can be as important as the content, a varied vocabulary is probably quite useful. But if your overriding goal in speech or writing is to communicate information, avoiding obscure words is usually a good idea. Of course, what counts as obscure will vary depending on the audience (if you’re speaking to mathematicians, words that are common in math papers but are obscure in typical english will, of course, be fine). But, generally speaking, words that are uncommonly used are less likely to be understand than common words, and even in cases when they have precise connotations that it would be useful to convey, those connotations may not be fully understood by your audience.
These considerations can lead us to an odd conclusion. If your goals prioritize communicating information over expressing yourself elegantly, you may actually be better off knowing fewer words. The trouble is that if you know obscure words well, you will be less likely to realize how obscure they are, and may use them automatically without even considering that others may misunderstand them. Having a large vocabulary is viewed, nearly universally, as a good thing, but in fact there can be negative consequences to making your vocabulary too large.
Before using an obscure word, ask yourself, “Is this really the clearest way to communicate what I’m trying to say?”