Sometimes an intermediate category is also included, variously called the body, belly, torso, or middle. This is used to describe the retailing strategy of selling many unique items with relatively small quantities sold of each (the 'long tail')-usually in addition to selling fewer popular items in large quantities (the 'head'). In business, the term long tail is applied to rank-size distributions or rank-frequency distributions (primarily of popularity), which often form power laws and are thus long-tailed distributions in the statistical sense. Note that there is no sense of the 'long tail' of a distribution, but only the property of a distribution being long-tailed. Intuitively, a distribution is (right) long-tailed if, for any fixed amount, when a quantity exceeds a high level, it almost certainly exceeds it by at least that amount: large quantities are probably even larger. In statistics, the term long-tailed distribution has a narrow technical meaning, and is a subtype of heavy-tailed distribution. The term is often used loosely, with no definition or an arbitrary definition, but precise definitions are possible.

The distribution could involve popularities, random numbers of occurrences of events with various probabilities, etc. In statistics and business, a long tail of some distributions of numbers is the portion of the distribution having many occurrences far from the 'head' or central part of the distribution. In this example, the cutoff is chosen so that areas of both regions are equal. To the right (yellow) is the long tail to the left (green) are the few that dominate. An example of a power law graph showing popularity ranking.

For the term used in statistics, see Heavy-tailed distribution. 'Long-tailed distribution' redirects here.

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