快速答案
manhã 指一天中的早晨，amanhã 指明天。
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
manhã
morning
Use manhã for the first part of the day.
amanhã
tomorrow
Use amanhã for the day after today.
如何选择
- manhã: Choose manhã if the sentence points to the first part of the day.
- amanhã: Choose amanhã if the sentence points to the day after today.
例句
Estudo de manhã.
I study in the morning.
A aula é amanhã.
The class is tomorrow.
常见误区
The initial a changes the meaning. Amanhã de manhã means “tomorrow morning” and uses both words.
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 manhã，一次用 amanhã。如果两个版本都可以，说明意思怎样变化。