before I go for a lie down中lie down前为何可以加a?
这里lie down是名词,一般应该带有连字符 lie-down。
牛津:[singular]
a short rest, especially on a bed
I’m going to have a lie-down before dinner.
所以,before I go for a lie down = before I go for a lie-down = before I go for a short rest.