It is correct, natural language isn't just English there is also many other kind too. But, the document is itself written in English, so we can guess that it is

It is correct, natural language isn't just English there is also many other kind too. But, the document is itself written in English, so we can guess that it is English. Still it doesn't help when you want to distinguish the natural language stuff dealing specifically English or in general (and if in general, you must be prepared to deal with stuff that is different from English, because they have their own features which are different from English).