right when you think that you have a language figured out, you realize there's a human side to the language and it's interpretation which means how the others read/hear it matters. therefore communication is not just about language, but about how to use it's constructs to say what you want to say and make sure that the other hears what you wanted to say.
what you say might be perceived in ways that you can't even imagine because you lack some information that the readers/listeners have, but they might not know that you don't know what they know. thus the act of speaking or writing becomes one of much more responsibility where you might want to consult experts about how you should put something into words. the experts can be people, good books, recordings of events, or anything which makes your writing/speech a living thing, one which doesn't need explainations afterwards.