A spider is a small creature with eight legs that spins silk webs to catch insects for food. Spiders aren't insects themselves (insects have six legs, not eight), but belong to a group called arachnids. They're found almost everywhere on Earth, from deserts to rainforests to your basement.

Most spiders are harmless to humans and actually help us by eating mosquitoes, flies, and other pests. A single spider might catch hundreds of insects in its lifetime. Some spiders build elaborate orb webs that glisten with morning dew, while others hunt actively without webs at all. The silk they produce is stronger than steel of the same thickness, making it one of nature's most remarkable materials.

While a few spider species have venomous bites that can harm people, most are too small or timid to pose any danger. Scientists have identified over 45,000 spider species, from tiny ones smaller than a pinhead to tarantulas as big as a dinner plate.

The word spider can also describe something that looks like a spider, such as a spider tripod used in photography, which has legs extending in different directions to hold a camera steady.