快速答案
fortuito 表示偶然且不可预见的事件；aleatório 表示无确定模式或随机选择方法。
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
fortuito
fortuitous or unforeseen
Use fortuito for happening by chance or outside reasonable prediction and control.
aleatório
random
Use aleatório for selected or occurring without a determined pattern, often by a random procedure.
如何选择
- fortuito: Choose fortuito if the sentence points to happening by chance or outside reasonable prediction and control.
- aleatório: Choose aleatório if the sentence points to selected or occurring without a determined pattern, often by a random procedure.
例句
O encontro fortuito mudou o rumo da pesquisa.
The chance encounter changed the course of the research.
A amostra foi escolhida de modo aleatório.
The sample was chosen randomly.
常见误区
A random sample is aleatória by design, not fortuita. A chance encounter is fortuito even without a statistical 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 fortuito，一次用 aleatório。如果两个版本都可以，说明意思怎样变化。