There are several types of fish. All of them are aquatic and have no limbs with digits. The main groups of fish are cartilaginous, bony, and extinct. These species are classified according to their body structure, such as gills or fins. In addition, some of them lack limbs at all. Here are the classifications for each type. In short, fish are animals that do not have limbs with digits.

The size of fish varies greatly. The smallest cyprinid in Indonesia grows to just 10 millimeters in length, while the whale shark Rhincodon typus is 12 meters long. As a result, there is a huge variety in size, composition, and structure among fish. Many species have unusual characteristics, such as being blind, producing electricity, and having a lateral line system that runs along their bodies.

While there are dozens of varieties of fish, there are only two species of whale sharks. Both are enormously large. The largest of them is a fifty-foot-long great whale shark. The smallest is the dwarf pygmy goby, which grows to about a third of an inch when fully grown. Some fish are able to glide, skip, and climb rocks, while others are able to produce electricity.

The word fish refers to a single species or pond. However, fishes is used for different species of a single species. Even though a pond may contain a mix of different kinds of species, the term fish is commonly used to describe all of them. The true fish, is the only type of fish that does not have movable parts. It is also referred to as a finfish when compared to other types of aquatic life.