If one talks to more than four people it is an audience, and one cannot really think or exchange thoughts with an audience.
Source: In The Speaker's Electronic Reference Collection, AApex Software, 1994.
-- Anne Morrow Lindbergh, (Jun 22 1906-2001), US writer; She wrote Listen! The Wind, 1938 and A Gift From the Sea, 1955, and was the wife of Charles Lindbergh.