Why are the leopard and cougar jaguar considered panthers?

Neither the leopard nor the cougar are considered panthers. The term "panther" is commonly used to refer to large felids such as lions, tigers, leopards, and jaguars. However, in the strict sense, the term "panther" refers only to the leopard (Panthera pardus) and the jaguar (Panthera onca). The cougar (Puma concolor), also known as the mountain lion, is not a panther.