system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: What is the purpose of eyebrows?
gpt
Shave your eyebrows and engage in some physical activity to find out.

One of the obvious functions of eyebrows is to keep sweat and other stuff from running into your eyes and interfering with your vision.

Other secondary functions involve communication and other social stuff. Having eyebrows makes it easier to see from a distance what is going on on someones face. It is just another thing to convey facial expressions more overtly.