A spider has eight legs. This characteristic is a defining feature of arachnids, the class of joint-legged invertebrates that includes not only spiders but also scorpions, ticks, and mites. The eight-legged anatomy of spiders allows for various adaptations, including efficient movement and the ability to spin webs. Spiders also have two main body segments: the cephalothorax and the abdomen. Their legs play a crucial role in hunting and capturing prey, as well as in locomotion and sensing their environment.