The worst thing that can happen to a student who is learning a foreign language is to get into the hands of people who are bent on studying curious and rare words that are not used in natural conversation:

“Many people share this idea that a language is “sophisticated” to the extent that it has a large vocabulary. In this view language is a store of words – the thicker the dictionary, the better the language. The kind of person who believes this usually delights in etymology or the collection of linguistic curios, rare words that no one ever uses in natural conversation [Greene, 2011: 127].