同位语从句是英语语法中的一个重要部分，其作用是进一步说明或解释前面的名词。在同位语从句中，常常会出现一些引导词，这些引导词的作用是引导同位语从句的开头。以下是同位语从句中常见的引导词：
- that
“that”是同位语从句中最常见的引导词，用于引导一个说明或解释前面名词的从句。例如：
- The fact that he failed the exam surprised everyone.
- I heard a rumor that they are getting married.
- whether
“whether”用于引导一个同位语从句，表示前面的名词所表示的事情是否成立。例如：
- The question of whether he will come or not is still unanswered.
- I am not sure about the weather and whether it will rain or not.
- who/whom
“who/whom”用于引导一个同位语从句，表示前面名词所表示的人的身份、职业或其他特征。例如：
- The man who/whom I met yesterday was very friendly.
- My sister, who/whom is a doctor, is going to work abroad.
- what
“what”用于引导一个同位语从句，表示前面名词所表示的事情的性质、特征或内容。例如：
- The problem is what we need to solve.
- I don't understand what you are talking about.
- if
“if”用于引导一个同位语从句，表示前面名词所表示的条件是否成立。例如：
- The question of if he will come or not is still unanswered.
- I am not sure about the weather and if it will rain or not.
以上是同位语从句中常见的引导词，掌握这些引导词可以帮助我们更好地理解英语语法中的同位语从句，提高我们的英语水平。
