"His publisher supplied him with a list of 400 words, ones that the publisher thought children would be learning in school. His publisher told him to cut the list in half and to try and write an interesting enough book for children. Nine months later Dr. Seuss finished The Cat In The Hat, which used 223 words from the list plus 13 words that did not appear on the list.
The story is 1626 words in length and uses a vocabulary of only 236 distinct words, of which 54 occur once and 33 twice. Only a single word – another – has three syllables, while 14 have two and the remaining 221 are monosyllabic. The longest words are something and playthings." Wickipedia