Abrasion (mechanical)

Abrasions are just like when you scratch your knee when you fall down, only it happens to things that are not alive, like rocks or metal. When two things rub against each other, sometimes they scratch or wear away a little bit.

Think of it like drawing on a piece of paper with a pencil. If you push too hard, the pencil can scratch the paper and take some of it off. That's similar to what happens with abrasion. When two things rub against each other, some of the surface of one or both things can be worn away or scratched off.

This is called mechanical abrasion because it happens because of physical force or motion – when something rubs against or scratches something else. So if you see a rock that has a rough, uneven surface or a piece of metal that's been scratched, it's probably because of mechanical abrasion.