Presenters: Meet the Gunning Fog Index
When they give presentations, their audiences may be equally brilliant, MBA-laden, rocket-scientist-level persons. BUT that doesn't exempt the presenters from being subject to the Gunning Fog index.
The Gunning Fog index is a measure of how well the written word will be understood by its intended audience. It measures (in English) by grade level. (I.e. If the Gunning Fog Index was "10", then the piece requires that someone has a 10th grade reading level to easily comprehend the piece.) This is measured by a combination of word length and familiarity. For universal understandability, most written pieces should have a Gunning Fox Index of 8, though many things can be understood up to level 12.
HOWEVER, comprehension is trickier with spoken word. We can read much faster than we can comprehend spoken language. When one is presenting at an event, the goal is to convey information and captivate the audience. The audience, therefore, shouldn't be expending subconscious (or conscious) brain power trying to figure out what you're trying to say. Comprehension is the first key to retention: the more they have to figure out WHAT you're saying, the less they'll remember.
A spoken presentation should be BELOW level 8.
So what's a presenter to do?
1. Not everyone understands your vernacular. Especially in niche-departments (i.e. engineering, marketing), colleagues can develop their own vernacular that is easily understood between close partnerships, but will be opaque to a broader audience. Use simple language, not cliches or corporate colloquialisms.
2. Run your speech through the Gunning Fog Index. You don't have to be precise or modify EVERY troubled word, but running your speech through the Gunning Fog Index (here's a quick tool) will give you a general idea of how tough your speech would be to understand.
3. Run your speech by your home partner or a colleague outside your department. If they get the gist of what you're saying, chances are your audience will too.
4. Simplification doesn't mean "dumbed-down". Seeking clear speech doesn't mean patronizing your audience. Giving examples, switching up your media, adding engagement, and simplifying your language will all keep your audience engaged without making them feel like your speech is a reiteration. There are certain things that are simple and captivating. Check out examples of How It's Made: These are complex processes that one would not necessarily find familiar--distilled to engaging components. Specialized terms are also explained.