0 words in general -- das Vokabular
1 (the stock of) words known and used eg by one person, or within a particular trade or profession -- der Wortschatz
the specialized vocabulary of nuclear physics.
He has a vocabulary of about 20,000 words
2 a list of words in alphabetical order with meanings eg added as a supplement to a book dealing with a particular subject -- das Wörterverzeichnis
This edition of Shakespeare’s plays has a good vocabulary at the back.