have a good time中的time是可数名词吗?为什么句子中出现“a”?

have a good time中的time是可数名词吗?为什么句子中出现“a”? "live"是可数名词吗?“time”当时间时,不是不可数名词吗?那怎么会有“have a good time what have a good time 中 time是可数还是不可数? have a good sleep中sleep是可数名词吗 时间time是不可数名词,那为什么有have a good time? 感叹句中什么时候用what和what a? have a good time 中的good time 不是不可数的吗? have a good time为什么加a have a good time. have a good time have a good time 其中time不可数为什么加a? 英语中command、time等不可数名词用形容词修饰时加a吗?例have a good time.ave a good have a fun time等于have a good time吗