快速答案
guardar 表示把东西留存起来；economizar 表示少用少花以节省资源。
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
guardar
to keep or set aside
Use guardar for retaining money or an object for future use.
economizar
to save by using less
Use economizar for reducing consumption or spending so resources remain.
如何选择
- guardar: Choose guardar if the sentence points to retaining money or an object for future use.
- economizar: Choose economizar if the sentence points to reducing consumption or spending so resources remain.
例句
Guardo parte do salário todo mês.
I set aside part of my salary every month.
Desligue a luz para economizar energia.
Turn off the light to save energy.
常见误区
You can guardar dinheiro without changing expenses. Economizar dinheiro specifically implies avoiding or reducing spending.
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 guardar，一次用 economizar。如果两个版本都可以，说明意思怎样变化。