核心问题
It's a part-time job, so I only work evenings.
如何分析句中的 evenings?
词典解答
可以把 evenings 看作是其前省略了介词 on 的介词短语。即(on) evenings 作时间状语：... so I only work(on) evenings.
也可以把 evenings 看作是名词, 直接作状语。类例:
-
(On) Sunday(s) we usually go for a walk. 我们通常在星期日出去散步。
-
I've got to work evenings! 我必须晚上工作!
[附注]有的英语词典把 evenings 定为副词。
Evenings, we sit at home and watch television. 晚上,我们坐在家里看电视。