The term "big cat" is used by zoologists to mean any of the five living members of the genus Panthera (the tiger, lion, jaguar, leopard, and snow leopard). In non-scientific contexts, "big cat" can also mean any member of the cat family that is considered "big", including animals like cheetahs and cougars that taxonomically fall under the small cats.
All cats are members of the Felidae family, sharing similar musculature, cardiovascular systems, skeletal frames, and behaviour. Both the cheetah and cougar differ physically from fellow big cats, and to a greater extent, other small cats. As obligate carnivores, big cats are considered apex predators, topping their food chain without natural predators of their own. Native ranges include the Americas, Africa, and Asia; the ranges of the leopard and tiger also extend into Europe, specifically in Russia.