three-day和three days的区别

都表示3天的意思，但是three days的前面是不能加a，而three-day可以。

如：

It's only threedays from today.

姶今天算起仅有三天。

British citizenscan enjoy a three-day stay for business or pleasure to 166 destinations withoutneeding a visa.

无需签证，英国公民可以在166个目的地待上三天进行商务或休闲活动。