An omnivore is a creature (including many humans) that consumes a varied diet of plant matter and meat, which may include flesh of other animals, fish, and insects, or the consumption of animal byproducts. Omni is from the Latin and translates as “all” or “everything” and the root word vore is related to the Latin term vorare, which means to consume or devour. It’s not far off to say that this is a create that eats everything, though plenty of omnivores are fairly picky about their diets.
The word is often contrasted with carnivore and herbivore. Carnivores typically have a diet of meat only, and herbivores tend to eat only plant matter. There can be a few variations.
For instance, a carnivore might eat grass or plants on rare occasions if it has an upset stomach or wants to induce vomiting. The terms tend to mean that these animals have meat or plant matter as their main diet the majority of the time. Following this logic, omnivores have a diet that is mainly composed of meat and plant matter, though a single meal could be exclusively meat or plant.
Humans are good examples of omnivore species, though the degree to which they eat more or less meats and plants may vary by finances, food availability, and location. Interestingly, some humans choose to become exclusively herbivores and are called vegans. Many vegetarians don't quite meet the herbivore definition, since they may eat animal byproducts, like dairy products, and may refer to themselves and ovo-lacto or lacto-ovo vegetarians. Though they don’t consume animal flesh, they do consume animal products.
Plenty of animals besides humans are omnivorous. Classic examples include many bear species, though polar bears are almost exclusively carnivorous. Many rodents, most pigs, and certain fish, like piranhas, eat both plants and meat. Though a species has the capacity to be omnivorous, it may not always be so. For instance, chickens can eat a variety of insects, other chickens, and various grains. Some are exclusively herbivores and are strictly grain fed, while others receive grain and fish meal. A few free-range chickens may have access to a few bugs or worms and may be mostly but not fully herbivorous.