The term big cat – which is not a biological classification – is used informally to distinguish the larger felid species from smaller ones. One definition of "big cat" includes the four members of the genus Panthera: the tiger, lion, jaguar and leopard. Members of this genus are the only cats able to roar. A more expansive definition of "big cat" also includes the cougar, cheetah, snow leopard and clouded leopard.

Despite enormous differences in size, the various species of cat are quite similar in both structure and behavior, with the exception of the cheetah, which is significantly different from any of the big or small cats. All cats are carnivores and efficient apex predators. Their range includes the Americas, Africa, Asia and Europe.

The ability to roar comes from an elongated and specially adapted larynx and hyoid apparatus. (However, neither the snow leopard nor the cheetah can roar, despite having hyoid morphology similar to roaring cats.) When air passes through the larynx on the way from the lungs, the cartilage walls of the larynx vibrate, producing sound. The lion's larynx is longest, giving it the most robust roar.

Big is a 1988 romantic comedy film directed by Penny Marshall and stars Tom Hanks as Josh Baskin, a young boy who makes a wish "to be big" to a magical wishing machine and is then aged to adulthood overnight. The film also stars Elizabeth Perkins, and Robert Loggia and was written by Gary Ross and Anne Spielberg.

Big was the latest, and most successful, of a series of age-changing comedies produced in the late 1980s; the others being: Like Father Like Son (1987), 18 Again! (1988), Vice Versa (1988), the Italian film Da grande (1987).

After being told he is too short for a carnival ride while attempting to impress an older girl (Kimberlee M. Davis), 12-year-old Josh Baskin (David Moscow) from Cliffside Park, New Jersey goes to a wishing machine called Zoltar Speaks, and wishes that he was "big." His wish is granted, but he finds out that the machine is unplugged, and backs away. By the next morning he is shocked to discover that he has been transformed into a 30-year-old man (Tom Hanks), and when he goes back to the wishing machine he finds that the carnival has already left. Fleeing from his mother (Mercedes Ruehl), who thinks he is a strange man who has kidnapped her son, Josh then finds his best friend, Billy Kopecki (Jared Rushton), at the school they both attend; Billy is shocked at first, but Josh convinces him of his identity by singing a secret song that only the two of them know. With Billy's help, he learns that it would take a couple of months to find the Zoltar Speaks machine, so Josh rents a flophouse room in New York City and gets a data entry job at MacMillan Toy Company.

The domestic cat (Felis catus or Felis silvestris catus, informally Felis domesticus) is a small, usually furry, domesticated, carnivorous mammal. It is often called the housecat when kept as an indoor pet, or simply the cat when there is no need to distinguish it from other felids and felines. Cats are valued by humans for companionship and ability to hunt vermin and household pests. They are primarily nocturnal.

Cats are similar in anatomy to the other felids, with strong, flexible bodies, quick reflexes, sharp retractable claws, and teeth adapted to killing small prey. As crepuscular predators, cats use their acute hearing and ability to see in near darkness to locate prey. Not only can cats hear sounds too faint for human ears, they can also hear sounds higher in frequency than humans can perceive. This is because the usual prey of cats (particularly rodents such as mice) make high frequency noises, so the hearing of the cat has evolved to pinpoint these faint high-pitched sounds. Cats also have a much better sense of smell than humans.