名词修饰常常由关系代词引导：Which That Who Whose Whom Where When
对于这些关系代词的使用有一定限制，例如：who 和whom 要修饰人，而which 则一定修饰物，而在GAMT的语法中,that 也不能修饰人，所以修饰人的词有Who, Whose or Whom ，而That 和 Which 则无法修饰人：
◆ Wrong: The scientists THAT made the discovery were rewarded.
◆ Right: The scientists WHO made the discovery were rewarded.
而Which 或whom 可以跟在介词后面:
the canal through which water flows; the senator for whom we worked.
Who 在从句中作主语，而whom 则作动词或介词的宾语：
◆ Wrong: The security guard WHO we met was nice.
◆ Right: The security guard WHOM we met was nice.
That 和 whom 从句中作宾语时可以省略：
◆ Right: The movie THAT we watched last Friday was scary.
◆ Right: The movie we watched last Friday was scary.
where可以用来修改地方名词，area, site, country or Nevada ，但是无法修饰“隐喻”地方的词如：condition, situation, case, circumstances, or arrangement，而要修饰这些词则应该用in which ：
◆ Wrong: We had an arrangement WHERE he cooked and I cleaned.
◆ Right: We had an arrangement IN WHICH he cooked and I cleaned.
When 可以指代事件或时间，如：period, age, 1987, or decade ，这里in which 也可以替换when.