broso

The interesting thing about broso is not the brush. It is which way the derivation runs, and this word is the standard example.

Esperanto roots have an inherent class, and the class decides what the other endings mean. A root whose basic idea is an action builds its tool with -il-: kombi is to comb, so the comb is kombilo. A root whose basic idea is a thing verbs directly into whatever you characteristically do with it: broso is a brush, so brosi is to brush. Two nearly identical objects, sitting on opposite sides of the fence, and nothing in the shape of either word tells you which side. The dictionary form is the only signal, and that is the honest asterisk on the promise that one root gives you four words for free. The -um wildcard and word-formation works the whole pattern through, including why marteli (to hammer) is real and krajoni is not.

So brosi is to brush, brosilo would be a tool for brushing and is therefore silly, and dentobroso is a toothbrush by ordinary compounding. Brosado is the act of brushing. All of that comes off one root once you know which way it faces.

The practical range is wide: hair, teeth, clothes, shoes, horses, paint. For the painter's brush you will also see peniko, which is the finer artist's tool, so a decorator has a broso and a portraitist has a peniko.