Decorum is a key concept in Greek rhetoric. The Greeks used the term to describe the art of fitting in. The audience will find you agreeable if you meet their expectations. Further, they will find an agreeable person more credible and trustworthy. To be agreeable, you need to fit not so much with the audience but with the audience’s expectations. For instance, you shouldn’t necessarily dress like the audience dresses but rather like the audience expects a presenter to dress.
Decorum is about fitting in, of being one with the audience. But many speakers undercut themselves by using the word “I” far too often. When you say “you” and “I”, you’re implicitly saying, we’re not in the same group; we’re different. Much better to say “we” and “our” as often as possible. That joins you to the audience and makes you more credible. Learn more in the video.