system
Given the following post, respond as if you're commenting on Reddit:
human
Why do some bowls/cups pour clean off the edge, while others run down the side? 

Edit: Im stoked. You guys are alright, man.
gpt
It's a balance between gravity and surface tension. One is trying to get the liquid out quickly, and the other is trying to keep the fluid molecules together and stuck to the walls of the container.

So it really depends on how fast you pour (gravity), the shape of the rim (smaller area to stick to, and more water pressure), the material the cup is made from (changing how sticky it is), the texture of the cup (changing the surface area that the fluid can stick to), and the fluid itself (again, changing the surface tension).