What I read long ago in a book on English:

TV vocabulary is targeted at 6th grade reading level.

Conversational English is about 2,000 words.

High school vocabulary is about 10,000 words.

College degree vocabulary is about 30,000 words

English has over a million words.

Which heartens me, because it means I can be "fluent" in another language by learning just 2,000 words.