职称英语中名词性从句是在句子中起名词作用的主谓结构，它可以在主从复合句中作主语、宾语、表语、介词的'宾语以及同位语。
主语从句主语从句可以由连词that，wh-疑问词或名词性关系词引导。
⑴由连词that引导：从句可以位于句首，但常常用形式主语it替代，从句本身则放在主句后面，如：
That he will come to the party is certain. It happened that the harvest was bad that year. Is it true that she has never been there?
通常在口语或非正式文体中，that常可省略，但必须是在用先行词it的情况下，如：
Its a pity you are leaving.
⑵由wh-疑问词引导：从句既可以前置，又可以借助于先行词it后置。如：
Who cleaned the meeting room is unknown. Its still a question when we shall have our sports meet. It is uncertain whether he will come.注意：在疑问句中，wh-疑问词所引导的从句不能位于句首，如：
Is it known where she went?
⑶主语从句也可由名词性关系词引导，这类从句只能位于句首，如：
Where she went was Los Angeles. What will be，will be. Whomever you invite will be welcome.
