As of September 2, 2007 when this chapter was written, there were an estimated 994,638 words in the English language (http://www.languagemonitor.com/). Everyone agrees that we are not born with the knowledge of these words and the rules by which they are strung together. A newborn child does not know or use any words. However, a child entering school has a lexicon of ∼ 13,000 words which, by the end of schooling, expands to ∼ 60,000 words and during adulthood reaches ∼ 120,000 words (Pinker 1999).