What is a "leech"?

A leech is a segmented, blood-sucking invertebrate that belongs to the class Hirudinea. It has a cylindrical body with a sucker at each end, enabling it to attach itself to the skin of its host. Leeches are typically found in freshwater environments such as ponds, swamps, and rivers. They use their powerful jaws to make small incisions in the skin and secrete an anticoagulant substance, allowing them to feed on the blood of their host. Despite their reputation as pests, leeches have been used in medicinal practices and for bloodletting in the past. They play a role in the ecosystem by helping to control populations of other organisms and by serving as a food source for various animals. Leeches have a remarkable ability to regenerate their body segments, which allows them to survive in diverse environments.