Financial Interest and Syndication Rules
The Financial Interest and Syndication Rules, i.e., fin-syn rules, were a set of rules imposed by the Federal Communications Commission (FCC) on the United States television industry in 1970. The FCC sought to prevent the Big Three television networks from monopolizing the broadcast landscape by preventing them from owning any of the programming that they aired in prime time.
Source: Wikipedia — Financial Interest and Syndication Rules (CC BY-SA 4.0)