快速答案
dever 可从建议到义务；ter de 和 ter que 表示实际需要，其中 ter que 在巴西尤其常见。
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
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.
如何选择
- 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.
例句
Você deve descansar.
You should rest.
Tenho de sair agora.
I have to leave now.
Tenho que trabalhar amanhã.
I have to work tomorrow.
常见误区
Context decides whether deve means should, must, probably is, or owes. Use ter de or ter que when obligation must be unmistakable.
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 dever，一次用 ter de。如果两个版本都可以，说明意思怎样变化。