A car is not an automobile (in a presentation)
One sure-fire way to lose the audience is to switch terminology in the middle of a presentation. You need to stick to one name for anything you are trying to represent. The USA is not the United States of America in a presentation unless you tell the audience it is.
You may want to invoke abbreviations after you introduce a concept. For example, suppose you want to use the term EMR for an Electronic Medical Record. The first time the concept appears on a slide it should look like the following: Electronic Medical Record (EMR). Now point to the words with your pointer and tell the audience that you will now be referring to Electronic Medical Records as EMRs. Anytime you switch nomenclature (which you should avoid as much as possible) tell the audience that you are doing that.
The same holds true for logos or any sort of visuals symbolizing a concept. Keep your terms and visuals as consistent as possible.