tax是税的意思，而rate则是税率的意思，区别可以从以下例子看出：

Our daughter paying so much tax, that is why I try to help to drop the tax rate legally, so she can save thousands dollars. 我们的女儿交了这么多税，所以我试图帮助合法地降低税率，这样她就可以节省数千元。