手早い答え
saber＋不定詞は方法を知ること、poder はその状況でできる・許されることです。
確実な見分け方は、英語から訳す前に、その単語の働きを見きわめることです。
それぞれの単語の働き
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.
選び方
- 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.
例文
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.
よくある落とし穴
English “can” may hide the difference: Eu sei dirigir describes the skill, while eu posso dirigir describes ability or permission in the situation.
文脈の中で練習する
自分の実生活から文を一つ選び、二回書いてみましょう。一度はsaberで、もう一度はpoderで。どちらも成り立ちそうなら、意味の違いを言葉にしてみましょう。