Erin knows that languages generally have a way to express numbers, that sentences generally contain multiple words, and that some languages use sounds that are not part of her native language. clearly, erin has what type of knowledge?
Erin has a Metalinguistic Knowledge. This type of knowledge consists of knowing and executing the linguistic knowledge of different languages, understanding the nuances of the codification of languages and comparing it, as well as being able to teach it to others.