For each cascade, the researchers determined the size (that is, the number of people involved in the cascade from start to finish), the depth (the number of retweets in a single, unbroken chain), the maximum breadth (the largest number of people who were part of the cascade at any depth), and the structural virality (a measure of the number of people who were responsible for helping a particular tweet spread). The more a rumor spreads, the more all four of these factors increase.

Source: Los Angeles Times March 08, 2018 22:52 UTC