Don’t try to sound smart.
The best teachers aren’t the ones who use big words. The best teachers know their subject so well that they can use terms that whomever they are talking with can understand. They “dumb it down” or “ratchet it up” to the degree of who their audience is. So, if they are talking with a high school student, they may use certain words, but will teach that same subject differently to a 25-year old or a 50-year old.
Isn’t it ironic that people who use complicated words to sound smart are actually showing that they don’t get it?
If you are teaching someone and you truly want to help that person understand, you need to stop making it about yourself. Don’t prop up your ego by using fancy words or technical jargon that the person you’re speaking to doesn’t understand. If you’re doing that, you either don’t know the subject well enough to speak in layman’s terms or you’re trying to boost your own self-esteem (hoping that they’ll be impressed with your “knowledge”).
Practice speaking in terms that your audience can understand. When you are able to help others understand the subject at hand, you are on your way to becoming a gifted teacher.