快速答案
lavar 指用水清洗；limpar 是让事物变干净的更广义说法。
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
lavar
to wash
Use lavar for cleaning with water, often with soap.
limpar
to clean
Use limpar for removing dirt by any method, with or without water.
如何选择
- lavar: Choose lavar if the sentence points to cleaning with water, often with soap.
- limpar: Choose limpar if the sentence points to removing dirt by any method, with or without water.
例句
Vou lavar as mãos.
I am going to wash my hands.
Preciso limpar a mesa.
I need to clean the table.
常见误区
You can limpar a stain without washing the whole object. Use lavar when the washing process itself matters.
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 lavar，一次用 limpar。如果两个版本都可以，说明意思怎样变化。