A division of reptiles called chelonia includes turtles, tortoises and terrapins. For the most part, the difference between a turtle and a tortoise is more of a matter of semantics than a strict scientific separation. Colloquially, both biologists and laypeople use the word "turtle" to mean all chelonians. In general, the reptiles referred to as turtles live in or near the water and have adapted to swim by holding their breath underwater. The reptiles referred to as tortoises typically live primarily in arid regions and are built for storing their own water supply and walking on sandy ground.
From a biological perspective, a tortoise is a kind of a turtle, but not all turtles are tortoises. Tortoises occupy their own taxonomic family, called testudinidae. All types of land and aquatic turtles come in a wide range of sizes, colors and shapes. Sometimes, the name "terrapin" is used to refer to an animal that falls somewhere between a turtle and a tortoise. Terrapins live in swampy areas or begin life underwater and eventually move to dry land.
Turtles can live on land but often live in freshwater, the ocean or brackish ponds and marshland. Their front feet might be fins or merely webbed toes, and they typically have streamlined back feet to help them swim. Some ways in which a turtle and a tortoise are different are that a turtle has a flatter back and might spend much of its life underwater.
A turtle typically mates and lays eggs on the shore. Some turtles sun themselves on logs, rocks or sandy banks. During cold weather, they often burrow in mud and go into a state called torpor, which is similar to hibernation. Sea turtles migrate great distances. They are often omnivorous, eating plants, insects and fish.
Tortoises live almost entirely above water. They typically wade into water only to clean themselves or to drink. In fact, they cannot swim and could drown in deep water. Unlike sea turtles, tortoises rarely migrate.
A tortoise's feet are hard, scaly and nubby so that it can crawl across sharp rocks and sand. Tortoises often have claws to dig burrows, which they occupy during hot, sunny weather or when they sleep. Their shell forms a rounded dome, allowing the tortoise's limbs and head to withdraw for protection.
Another difference between a turtle and a tortoise is that a tortoise is mostly herbivorous. It typically eats grasses, flowers and weeds. Tortoises also eat shrubs, cacti and other plants that have a lot of moisture. They sometimes eat fruit and leafy greens, especially in captivity. Some tortoises also eat insects, worms and carrion.