for the weekend与for a week的区别

for the weekend这个短语不常见，通常情况下介词for后面应该加上一段时间，因此for a week才是常用的短语。

for a week表达的意思是“（动作持续了）一段时间”，如：They're going to stay in Shanghai for a week. 他们打算在上海待一星期。They have been in Shanghai for a week