Google Books Ngram Viewer

Warning The Ngram viewer currently displays English hyphenated word frequencies incorrectly if used with default settings. To avoid this, append :eng_2019 to each term, and use the "square bracket with spaced hyphen" format. For example, to compare frequencies of "tonight" and "to-night", instead of entering tonight,to-night you need to enter tonight:eng_2019,[to - night]:eng_2019

The Google Books Ngram viewer displays graphs showing how frequently given words or phrases have occurred in a corpus of books over time. It is particularly helpful when investigating ambiguous spelling or hyphenation of words during PPing.

To use it, type the terms you want to compare - SEE WARNING ABOVE - separated by commas, into the entry field on the webpage and click the search icon or press return/enter. Example output below.

Example graph comparing "tonight" and "to-night"