I remember running into a well-meaning person who heard the linguistics lecturer use the term “natural language” and tried to object that no language or dialect is actually more natural — that is, “better” in some way, or more suited to learning — than any other. Which is something that audience would not disagree with, in general, among the set of languages they were discussing. (Which of course, were just those natural languages.)
But of course there are several ways some communication system or notation system can be called a language but is not a natural language. Roy’s list includes two major types, and misses a couple other categories. (But we don’t get to hear if he has command of other natural languages.)
Here’s an amusing talk I ran across recently, which may be fun for those with either practical programming experience in a few different computer languages or anyhow a reading/browsing acquaintance with them.