A carnivore /ˈkɑːrnɪvɔːr/, or meat-eater (Latin, caro, genitive carnis, meaning meat or "flesh" and vorare meaning "to devour"), is an animal whose food and energy requirements derive solely from animal tissues (mainly muscle, fat and other soft tissues) whether through hunting or scavenging.

Animals that depend solely on animal flesh for their nutrient requirements are called hypercarnivores or obligate carnivores, while those that also consume non-animal food are called mesocarnivores or facultative carnivores.

Omnivores also consume both animal and non-animal food, and apart from the more general definition, there is no clearly defined ratio of plant vs. animal material that would distinguish a facultative carnivore from an omnivore.

A carnivore at the top of the food chain, not preyed upon by other animals, is termed an apex predator.

Obligate or "true" carnivores are those whose diet requires nutrients found only in animal flesh. While obligate carnivores might be able to ingest small amounts of plant matter, they lack the necessary physiology required to fully digest it.

Some obligate carnivorous mammals will ingest vegetation as an emetic, to self-induce vomiting the food that upset its stomach.

A hypercarnivore is an animal which has a diet that is more than 70% meat, either via active predation or by scavenging. The remaining non-meat diet may consist of non-animal foods such as fungi, fruits or other plant material.

Some extant examples of hypercarnivorous animals include crocodilians, owls, shrikes, eagles, vultures, felids, most wild canids, dolphins, snakes, spiders, scorpions, mantises, marlins, groupers, piranhas and most sharks. Every species in the family Felidae, including the domesticated cat, is a hypercarnivore in its natural state. Additionally, this term is also used in paleobiology to describe taxa of animals which have an increased slicing component of their dentition relative to the grinding component.

Hypercarnivores need not be apex predators. For example, salmon are exclusively carnivorous, yet they are prey at all stages of life for a variety of organisms. Characteristics commonly associated with carnivores include strength, speed, and keen senses for hunting, as well as teeth and claws for capturing and tearing prey. However, some carnivores do not hunt and are scavengers, lacking the physical characteristics to bring down prey; in addition, most hunting carnivores will scavenge when the opportunity arises. Carnivores have comparatively short digestive systems, as they are not required to break down the tough cellulose found in plants.

Many hunting animals have evolved eyes facing forward, enabling depth perception. This is almost universal among mammalian predators, while most reptile and amphibian predators have eyes facing sideways.

A special adaptive feature lies in the fourth upper premolar and the first lower molar, specialized teeth that form shearing blades to cut up meat guillotine fashion. These cutting teeth, called carnassials, are common to meat-eating Carnivores who kill large prey. They shear off small chunks of meat and swallow it whole, rather than chewing it. Many cats have a rasp-rough tongue that can literally lick the meat off of bones. Carnassials are least developed in those species whose diets have become less carnivorous, and the aquatic members of the order lack carnassials, either swallowing the prey whole or ripping it into smaller parts.

The carnivores have strong jaws, powerful muscles, and heavy skulls to put their teeth into action. Among the strongest jaws are the Jaguar of South America, which can bite through a turtle’s shell, and the hyena of Africa, which can bite through bones to get to the bone marrow inside.

A herbivore is an animal anatomically and physiologically adapted to eating plant material, for example foliage or marine algae, for the main component of its diet. As a result of their plant diet, herbivorous animals typically have mouthparts adapted to rasping or grinding. Horses and other herbivores have wide flat teeth that are adapted to grinding grass, tree bark, and other tough plant material.

There are many different types of herbivores. Many eat a variety of plants, while some stick to one type of plant. Those who stick to one type of plant have their own special classifications. For example, animals that eat primarily fruit are called frugivores, according to Encyclopedia Britannica. Fruit bats and flying foxes are examples of frugivores. And, animals and insects that eat mostly leaves — such as pandas, caterpillars, giraffes or koalas — are called folivores.

Animals that eat wood exclusively or almost exclusively are called xylophages. Termites and Asian long-horned beetles are examples of xylophages. Contrary to popular belief, beavers are not xylophages. In addition to wood they also consume leaves, roots and aquatic plants.

The digestive systems of carnivores and herbivores are very different. Carnivores typically have only one stomach chamber and a simple digestive system. Herbivores can often have several stomach chambers and a much longer digestive tract. Herbivores with multiple stomach chambers — such as camels, deer, sheep, giraffes and cattle — are called ruminants.

“Plant cells are tough, and the cellulose that makes up their cell walls is difficult to digest,” said McCarthy. Digestion starts with the teeth. Herbivores have large, flat teeth that grind up plant materials. In contrast, carnivores have mostly sharp, pointed teeth that are used for tearing flesh. Once the plant materials are chewed, special bacteria in the gut of an herbivore and the longer digestive tract break down the plant material.

Ruminants regurgitate food and rechew it to help with the digestive process. This regurgitated food is called cud. After swallowing the cud, it travels to the second stomach chamber. After it softens, the cud goes back up to be chewed again and then goes down to the third chamber. This keeps happening until the cud has made its way through all of the stomach chambers, according to National Geographic.

The herbivores do the hard job of processing the energy that comes from plant life, which makes them much easier to digest for the carnivores. “This is why we will see a much shorter and less complicated digestive system in an obligate carnivore like a tiger versus a true ruminant such as a cow,” said McCarthy.