All three of the terms introvert, extrovert, and extravert can refer to a person with a certain personality type. One type is a little more reserved in conversation, especially with large groups, and the other type is more gregarious. And one type has some debate over the correct spelling of the term.
So let's look at the meanings and spellings of introvert, extrovert, and extravert in this post.
Introvert vs. Extrovert vs. Extravert
Introvert can be used as a noun or verb. As a verb, introvert means to turn in on or direct toward itself. As a noun, introvert refers to a more reserved person, especially when it comes to conversation. While many introverts are considered shy, this is not always the case. However, most introverts are drained by big social events, even if they enjoy them, especially if they are the center of attention.
Extrovert is a noun for a person who is generally outgoing and unreserved with their speech. Whereas small talk and group settings can tend to drain introverts, extroverts usually thrive on such settings. Most will seek out the spotlight and love to take part in conversations.
Extravert, on the other hand, is another way of saying extrovert that was originally used by Carl Jung. In fact, here's a piece from Scientific American, in which the author argues for using extraversion over extroversion, while also digging deeper into why there are two different spellings and what extra- or extroversion means. Those arguments aside, it appears the most common and proper way to use the term outside of technical journals is with the "o," though who knows; maybe this will develop into an Oxford comma situation.
Examples of Introvert, Extrovert, and Extravert:
Correct: She must be an introvert, because she talked very little and retired to her room before the party was over.
Incorrect: She must be an extrovert, because she talked very little and retired to her room before the party was over.
Incorrect: She must be an extravert, because she talked very little and retired to her room before the party was over.
Correct: He's such an extrovert—always gathering a crowd and introducing himself to strangers.
Technically correct: He's such an extrovert—always gathering a crowd and introducing himself to strangers.
Incorrect: He's such an introvert—always gathering a crowd and introducing himself to strangers.
A final note on introvert, extrovert, and extravert:
There are so many more levels of meaning to peel back on introverts and extroverts, and it's my goal to eventually have a series on just that topic. But in the meantime, it's good to know the surface level difference.
How I keep them separate in my head is that the "i" in "introvert" represents a solitary person who prefers to recharge alone, while you need the first "e" from "extrovert" to spell "we," which is the type of multi-person situation in which extroverts thrive.
Outside of technical journals and psych classes, extrovert is more commonly preferred over extravert. A good way to keep that straight is the consistency of the "o" in "intrOvert" and "extrOvert."
No matter what type of writing you do, mastering the fundamentals of grammar and mechanics is an important first step to having a successful writing career.