The collection of series, instances of which are Groups of Events, each member of which is separated from the other by a non-trivial time. Some instances are Events in their own right, such as Major League Baseball's World Series, which is also a series of (at most) seven distinct events with many hours between them. Some instances are not Events, such as a series of heart attacks suffered by 'Bob' between 1997 and 1998. Non-examples include breathing events, which are generally continuous strings of breathing subevents.