快速答案
só 既可表示“仅仅”，也可表示“独自”；apenas 只表示“仅仅”。
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
só
only or alone
Use só for restriction in everyday speech, or being without company.
apenas
only or merely
Use apenas for neutral restriction of an amount, fact, or action.
如何选择
- só: Choose só if the sentence points to restriction in everyday speech, or being without company.
- apenas: Choose apenas if the sentence points to neutral restriction of an amount, fact, or action.
例句
Hoje eu estou só.
Today I am alone.
Tenho apenas dez reais.
I have only ten reais.
常见误区
The adjective só changes for plural when it means alone: elas estão sós. The adverb meaning only does not change.
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 só，一次用 apenas。如果两个版本都可以，说明意思怎样变化。