快速答案
tudo 独立使用，表示“一切”；todo 通常修饰名词，并与之保持性数一致。
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
tudo
everything
Use tudo for all things in general, without a noun after it.
todo
every or all of
Use todo for a complete set or each member, normally with a noun.
如何选择
- tudo: Choose tudo if the sentence points to all things in general, without a noun after it.
- todo: Choose todo if the sentence points to a complete set or each member, normally with a noun.
例句
Tudo está pronto.
Everything is ready.
Todo aluno tem um livro.
Every student has a book.
常见误区
Do not say tudo dia for “every day.” The natural phrase is todo dia or todos os dias.
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 tudo，一次用 todo。如果两个版本都可以，说明意思怎样变化。