快速答案
mesmo 表示同一个对象；igual 比较彼此相同或相似的不同对象。
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
mesmo
same or very one
Use mesmo for identity: the exact person, thing, place, or repeated item.
igual
equal or alike
Use igual for two different things with matching qualities, value, or appearance.
如何选择
- mesmo: Choose mesmo if the sentence points to identity: the exact person, thing, place, or repeated item.
- igual: Choose igual if the sentence points to two different things with matching qualities, value, or appearance.
例句
Usamos o mesmo livro.
We use the same book.
Nossas bolsas são iguais.
Our bags are alike.
常见误区
Duas camisas iguais are two similar shirts; a mesma camisa is one and the same shirt.
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 mesmo，一次用 igual。如果两个版本都可以，说明意思怎样变化。