In the preface to the third book, Thorndike writes that the list contained therein "tells anyone who wishes to know whether to use a word in writing, speaking, or teaching how common the word is in standard English reading matter" (p. x), and he further advises that the list can best be employed by teachers if they allow it to guide the decisions they make choosing which words to emphasize during reading instruction. Some words require more emphasis than others, and, according to Thorndike, his list informs teachers of the most frequently occurring words that should be reinforced by instruction and thus become "a permanent part of [students’] stock of word knowledge" (p. xi). If a word is not on the list but appears in an educational text, its meaning only needs to be understood temporarily in the context in which it was found, and then summarily discarded from memory.