手早い答え
dever は助言から義務まで、ter de と ter que は実際上の必要を表し、ブラジルでは ter que が特に一般的です。
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
dever
should, must, or owe
Use dever for advice, duty, expectation, probability, or a debt.
ter de
to have to
Use ter de for necessity or obligation in neutral and careful language.
ter que
to have to
Use ter que for necessity or obligation in very common Brazilian speech.
選び方
- dever: Choose dever if the sentence points to advice, duty, expectation, probability, or a debt.
- ter de: Choose ter de if the sentence points to necessity or obligation in neutral and careful language.
- ter que: Choose ter que if the sentence points to necessity or obligation in very common Brazilian speech.
例文
Você deve descansar.
You should rest.
Tenho de sair agora.
I have to leave now.
Tenho que trabalhar amanhã.
I have to work tomorrow.
よくある落とし穴
Context decides whether deve means should, must, probably is, or owes. Use ter de or ter que when obligation must be unmistakable.
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deverで、もう一度はter de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。