快速答案
afim 是表示“相关的”的形容词；a fim de 是表示目的的三个词。
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
afim
related, similar, or by affinity
Use afim for ideas, fields, people, or relatives connected by similarity or affinity.
a fim de
in order to
Use a fim de for introducing a purpose or intended result.
如何选择
- afim: Choose afim if the sentence points to ideas, fields, people, or relatives connected by similarity or affinity.
- a fim de: Choose a fim de if the sentence points to introducing a purpose or intended result.
例句
As duas pesquisas tratam de temas afins.
The two studies address related topics.
A equipe se reuniu a fim de revisar o plano.
The team met in order to review the plan.
常见误区
When para can replace the expression, write a fim de separately. The informal estar a fim de also remains separate.
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 afim，一次用 a fim de。如果两个版本都可以，说明意思怎样变化。