手早い答え
diminuir は小さくなること、reduzir は意図的に低い水準へ下げることを表しがちです。
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
diminuir
to decrease, lessen, or become smaller
Use diminuir for a quantity, sound, speed, pain, or intensity going down.
reduzir
to reduce or cut
Use reduzir for deliberately bringing a quantity, cost, risk, or scope down to a lower level.
選び方
- diminuir: Choose diminuir if the sentence points to a quantity, sound, speed, pain, or intensity going down.
- reduzir: Choose reduzir if the sentence points to deliberately bringing a quantity, cost, risk, or scope down to a lower level.
例文
A chuva diminuiu à tarde.
The rain eased in the afternoon.
Precisamos reduzir o desperdício.
We need to reduce waste.
よくある落とし穴
Both can be transitive or intransitive in many contexts. Reduzir sounds more planned or technical; diminuir is broader in daily speech.
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diminuirで、もう一度はreduzir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。