New Ideas, New Words
It is true, however, that an educated person should never rest content with the size of his usable speaking vocabulary. The addition of every new word is likely to indicate the grasp of a new idea. Likewise, every new idea is almost certain to require its individual terms for expression. An enlarging vocabulary is the outward and visible sign of an inward and intellectual growth.
No man's vocabulary can equal the size of a dictionary, the latest of which in English is estimated to contain est. some 1,000,000 words. Life may be maintained upon a surprisingly meager group of words, as travelers in foreign lands can testify. Shakespeare's vocabulary is said to have included as many as 15,000 words. Figures for that of the average person vary considerably.