快速答案
taxa 常指比率或费用；tarifa 指服务的固定收费价格。
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
taxa
rate or fee
Use taxa for a percentage, measured rate, or charge connected to a service or public act.
tarifa
service fare or tariff
Use tarifa for the set price charged for transport, utilities, or another priced service.
如何选择
- taxa: Choose taxa if the sentence points to a percentage, measured rate, or charge connected to a service or public act.
- tarifa: Choose tarifa if the sentence points to the set price charged for transport, utilities, or another priced service.
例句
A taxa de juros caiu neste mês.
The interest rate fell this month.
A tarifa de ônibus aumentou.
The bus fare increased.
常见误区
Official charges follow legal definitions, so do not freely rename a tarifa as taxa in contracts, taxes, or public notices.
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 taxa，一次用 tarifa。如果两个版本都可以，说明意思怎样变化。