快速答案
chão 是人站立的地面或地板；piso 常强调铺设的材料或饰面。
可靠的方法是先判断这个词在句子里的功能，再翻译。
每个词的作用
chão
ground or floor
Use chão for the surface people stand on, indoors or outdoors.
piso
flooring or paved surface
Use piso for the built material or finish covering a floor.
如何选择
- chão: Choose chão if the sentence points to the surface people stand on, indoors or outdoors.
- piso: Choose piso if the sentence points to the built material or finish covering a floor.
例句
O copo caiu no chão.
The glass fell on the floor.
Vamos trocar o piso do banheiro.
We are going to replace the bathroom flooring.
常见误区
They overlap indoors, but trocar o chão sounds broader than trocar o piso, which clearly points to the floor covering.
放到语境中练习
从你的真实生活中选一个句子，写两遍：一次用 chão，一次用 piso。如果两个版本都可以，说明意思怎样变化。