According to Jewish numerology, the word "chai" (meaning "life") adds up to 18, so in Jewish traditions, 18 is considered a lucky number. Donations to charities or gifts to bat / bar mitzvah children, marrying couples, and new babies are often made in increments of 18 for this reason. The word "chai" might be familiar to even non-Jewish people from the toast "L'chaim" (meaning "to life!"), the inspiration for an eponymous song from the hit 1964 Broadway musical Fiddler on the Roof.