快速答案
andar 是日常说法中的楼层；piso 通常指地面表面或铺装材料。
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
andar
storey or floor level
Use andar for a level of rooms in a building.
piso
floor surface or level
Use piso for the material underfoot, and in formal contexts a building level.
如何选择
- andar: Choose andar if the sentence points to a level of rooms in a building.
- piso: Choose piso if the sentence points to the material underfoot, and in formal contexts a building level.
例句
Moro no terceiro andar.
I live on the third floor.
O piso da cozinha é de madeira.
The kitchen floor is wood.
常见误区
O terceiro piso is possible, especially in formal naming, but andar is the safer everyday choice for where an apartment is.
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 andar，一次用 piso。如果两个版本都可以，说明意思怎样变化。