A forelimb is a front leg or arm of an animal. Your own arms are your forelimbs, while your legs are your hind limbs. A dog's front legs are its forelimbs, and a bird's wings are actually modified forelimbs adapted for flight instead of walking.

Scientists use this term when comparing how different animals are built. Even though a bat's wing, a whale's flipper, a horse's front leg, and your arm look completely different and do different jobs, they're all forelimbs with surprisingly similar bone structures inside. They all have the same basic parts: a single upper bone, two lower bones, and several smaller bones at the end. This similarity exists because these animals all evolved from ancient ancestors with the same basic body plan.

Understanding forelimbs helps scientists see how evolution works. A seal's flipper didn't appear from nowhere: it's a forelimb that changed over millions of years to work better for swimming. The same pattern appears across the animal kingdom, showing how nature adapts the same basic structures for different purposes. What works for digging (a mole's forelimbs) looks nothing like what works for climbing (a monkey's forelimbs), yet both started with the same blueprint.