In his book Comedy Writing Step by Step, Gene Perret, one of the best known comedy writers in Hollywood, says, "A joke is anything that makes people laugh. It can be a series of words, a look, a shrug of the shoulders, even a moment of silence but if it makes people laugh, it's a joke."
I agree with Gene, but I try to avoid using the term joke when training people to do presentations. Here's why. When I ask my seminar participants for a show of hands of who can tell a joke, only a few people raise their hands. In fact, most people claim they can't tell a joke. Their claim indicates to me that they are simply not practiced and are maybe a little afraid of the term itself. I assure them that using humor in professional presentations is NOT about telling jokes. It's about using many easily implemented forms of humor to help attain the goals of a presentation.
This highfalutin explanation is usually enough to distract them so I can teach them how to tell jokes. Consequently, you won't see me using the word joke very much in this book. I'm too busy teaching you how to make people laugh.
If you like to tell jokes there are presently 97.5 zillion joke books available on every topic in the world. Acquire the ones you like and pick appropriate jokes to help you make the points of your presentation.
Use humor to make more money as a public speaker!