快速答案
saber＋不定式表示知道怎么做；poder 表示当下能够做或被允许做。
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
saber
to know how
Use saber for a skill or procedure someone has learned.
poder
can or may
Use poder for present ability, possibility, or permission.
如何选择
- saber: Choose saber if the sentence points to a skill or procedure someone has learned.
- poder: Choose poder if the sentence points to present ability, possibility, or permission.
例句
Eu sei nadar.
I know how to swim.
Hoje não posso nadar porque a piscina está fechada.
Today I cannot swim because the pool is closed.
常见误区
English “can” may hide the difference: Eu sei dirigir describes the skill, while eu posso dirigir describes ability or permission in the situation.
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 saber，一次用 poder。如果两个版本都可以，说明意思怎样变化。