Google Ngram ViewerAllows users to search for specified terms or phrases in a collection of the books digitized for Google Books, and then graphs the frequency of occurrence over time. Phrases may contain a maximum of five words or "ngrams." Trends can be viewed as a moving average by applying a "smoothing" value that averages the data for a specified number of years on either side of the target year, and often makes trends more apparent. In addition, users may automatically search the entire Google Books corpus for the terms or phrases by selecting one of the year ranges.