I know that word: What does vocabulary mean?

     There is certainly a close connection between the word vocabulary and the word word, which is perhaps why some people think that vocabulary means "a word". Of course, we do want to make a distinction between the ideas of vocabulary and word, so some people might expand their definition to say that vocabulary means "a word that has a meaning," or that vocabulary means "a word which is used to communicate." However, there is a basic problem with this sort of definition of the noun vocabulary:  it does not fit some clear examples. For example, when we ask someone, "How large is your English vocabulary?", it is clear that the answer is large number of words, varying from a few hundred for a beginning learner of English to perhaps 25,000 for a well educated native speaker of English. Similarly, if we ask, "How large is the English vocabulary?", the answer is a very large number indeed. The Oxford English Dictionary (OED) lists more than 200,000 distinct words in the English vocabulary, and if different senses of the words "were counted, the total would probably approach three quarters of a million." ("How Many Words", 2013). We also commonly speak of the legal vocabulary as being different to the vocabulary of ordinary conversational English, meaning that English used by lawyers, judges and other legal experts uses words that are not in normal use by people going about their daily business. The justices of the United States Supreme Court, for example, regularly use the word comport in their highly influential opinions on questions of American law, but this word is not in common use amongst ordinary users of English: it is part of the specialised vocabulary of the legal profession. Similarly, the eighth edition of the Oxford Advanced Learner's Dictionary (OALD) indicates with a mortar board symbol which words are important for an academic English vocabulary, which is distinct from their key symbol marking for essential English vocabulary for learners of English. In the case of the word academic, for example, the OALD tells us that it is a word important both for key English vocabulary and for academic English vocabulary. In contrast, the OALD tells us that the verb comport is neither a part of the key English vocabulary that learners need know nor essential for academic vocabulary. And so specific to the legal vocabulary is the sense of comport as regularly used by US Supreme Court justices that that definition is not even recorded in the OALD. The common definition in legal contexts of comport as meaning "to agree with, accord with" is listed as definition number 5 in the massive and extremely comprehensive OED. What does this tell us about the meaning of the word vocabulary? It tells us that vocabulary means not "a word" but "a group of words."

    However, these examples of how English speakers use the word vocabulary do more than correct a common misunderstanding that vocabulary means "a word": they also suggest that  it is something in use by a person or group of persons, and it might be limited to a particular context. As the context varies, for example from a conversation with friends about the latest reality TV show to the opinions of the US Supreme Court, so too does the vocabulary vary; that is, the people in those groups share different collections of words which they regularly use to communicate their ideas to others. One more example might help: on a recent trip home to Australia, my teenage nieces and nephews kept describing places and things as being "bogan," a word that I had never heard, and certainly never used, but which is clearly a regular part of their vocabulary, if entirely lacking in mine. To my surprise, this word bogan is in fact listed in the OALD, with a note advising that it is used informally, and that it is generally restricted to the English vocabulary or Australians and New Zealanders, although my teenage nieces and nephews, and I am sure their social group generally, has expanded the meaning beyond what is currently recorded in the OALD. The OED is bit more informative on bogan, with illustrative quotation up to 2011, but it also fails to record what appears to be a much more recent extension of meaning to places, things and activities amongst Australian teenagers, who might say, for example, that "We can't go there; that's so bogan!" which is certainly not something I would say: if I did, none of my friends would understand me. I would be very surprised if an American or Briton knew the  word bogan. The word vocabulary, then, basically means "the set of words used by a person or group of people, sometimes in a specific context," which definition comports with the first three definitions of vocabulary as listed in the OALD.

__________

Reference

How many words are there in the English language? (2013). Retrieved from Oxford Dictionaries website: http://oxforddictionaries.com/words/how-many-words-are-there-in-the-english-language