I consider myself a fairly adept communicator. And, yet often I try to communicate important details to people, and they prove to me that I can't explain anything to them clearly.
The problem with communications, language, and syntactical observance, is that people don't hear words, language, structure, or truth. They hear with their emotions, their bigotry, and their desires both good and bad. You can explain a fact to a man as many ways as possible, and he will still only understand that which he is willing to comprehend.
People hear what they want to hear.
My failure tends to be adjusting my speech for emotion. People want to hear something, often they want to be angry. So, even agreeing with them sounds like fighting words. Or, they don't want to learn something. So, no matter how you clarify what you're trying to say, they want to hear something so confusing, they can't possibly comprehend. I deal with this every day in customer relations and technology support.
Sometimes the words and inflection are the same, but meaning is completely different. One customer says agrily, "I don't understand." And, that means they desire help. Another says the same thing, the same way, and they are expressing a personal dislike for the person they are talking to. They may actually desire to terminate the relationship and don't actually want to learn anything.
I've finally come to understand one fact of communications. Sometimes people don't want to hear you, and when people don't want to do something they most often don't.
That may sound like a cop out. But, the fact is, it's a very important lesson in communication. When you realize that someone doesn't want to learn, hear, or understand, it's wasteful and often destructive to continue trying. Often one of the best steps toward better communication is to realize that your audience doesn't want knowledge. They have a position, ignorant or not, and they will not budge. The only way to handle the situation is to accept their position and move around them.