The term for erosion caused by stones in a river is abrasion.

Here's a breakdown:

* Abrasion: This is a type of erosion where rocks and sediment carried by the river (like pebbles and sand) grind against the riverbed and banks, wearing them down over time.

Think of it like sandpaper: the stones act as the sandpaper, and the riverbed and banks are the material being smoothed out.