快速答案
chance 常表示可能性；oportunidade 表示可采取行动的有利时机。
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
chance
chance or probability
Use chance for the possibility that something will happen, sometimes also a favorable opening.
oportunidade
opportunity
Use oportunidade for a favorable moment or set of conditions for doing something.
如何选择
- chance: Choose chance if the sentence points to the possibility that something will happen, sometimes also a favorable opening.
- oportunidade: Choose oportunidade if the sentence points to a favorable moment or set of conditions for doing something.
例句
Há uma boa chance de chuva.
There is a good chance of rain.
Ela recebeu uma oportunidade de trabalho.
She received a job opportunity.
常见误区
The words overlap in “give someone a chance.” With probability, only chance fits naturally; with a concrete opening, oportunidade is more precise.
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 chance，一次用 oportunidade。如果两个版本都可以，说明意思怎样变化。