快速答案
impugnar 正式挑战有效性或可受理性；contestar 更广泛地表示争议或反对。
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
impugnar
to formally challenge
Use impugnar for attacking the validity, admissibility, or correctness of an act, document, candidate, or evidence.
contestar
to dispute or answer a claim
Use contestar for opposing an assertion or decision, including responding to a legal action.
如何选择
- impugnar: Choose impugnar if the sentence points to attacking the validity, admissibility, or correctness of an act, document, candidate, or evidence.
- contestar: Choose contestar if the sentence points to opposing an assertion or decision, including responding to a legal action.
例句
O partido impugnou a candidatura.
The party challenged the candidacy.
A empresa contestou os valores cobrados.
The company disputed the amounts charged.
常见误区
Not every disagreement is an impugnação. The formal remedy usually requires a defined object and procedure.
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 impugnar，一次用 contestar。如果两个版本都可以，说明意思怎样变化。