There are so many languages within English. And I don't mean how we absorb foreign words and phrases. I mean when using nothing but English, there are countless ways to speak. A common example is the difference between how you talk to your friend and how you talk to your parents/your boss/the police.
But there is so much more than that. I easily have a half dozen interests: writing, music, technology, martial arts, philosophy, chemistry. I will immediately admit that some of these subjects I have WAY less knowledge on than others. But they are all my interests. And if I am talking with somebody who also shares a particular interest, we share its language.
Vocabulary is certainly a large part of it, but a language is more than just its words. The things you talk about, the way you view the world, the ideas and the ideals that you hold depend upon the subject you discuss, and the language reflects that.
In music, we think about aural quality. The vocabulary is based on the qualities of sounds and the ideals are based on what is most pleasant to the ears. Admittedly, different musicians have different opinions on what is pleasant, but in general, fitting into standard rhythmic patterns and playing in tune are highly valued.
In martial arts, the primary goal is to survive. The language surrounds the idea of control. Minds need to be focused. The body needs to be balanced. You may hear a compliment like, "that looked good" just as commonly as "that looked strong", but the reason is that a trained martial artist can see when a technique has power behind it. Something looks aesthetically good because they can see the power and control in it. Again, different people hold different beliefs when it comes to martial art ideals, so take that as one example.
Although I only speak English fluently, I sometimes feel like I am multilingual. I can switch between completely different language sets. A conversation with one friend might be gibberish to another. Fortunately, as an expert communicator, I am also simultaneously learning how to explain and teach any of those languages to any person, no matter how much they do or don't know about the subject.