求第一、第二、第三条件句详解

注意：If 引导的一般从句和第一条件句较容易理解.
第二和第三条件句都是虚拟语气,不同的是,第三条件句是表达和过去相反的条件句.
常见第二条件句的例子就是,If I were you, I would.
常见第三条件句的例子就是,If I had done, I would have.
零条件句Zero Conditional
意义：用于阐述事实.
结构：If + subject + simple present, subject + simple present.
Subject + simple present if + subject + simple present.
例句：If I see a spider, I get panicky.
I feel claustrophobic and immediately want to get out of if I enter an enclosed space.
第一条件句First Conditional
意义：表达一个动作后的结果
结构：If + subject + simple present, subject + will + verb.
Subject + will + verb + if + subject + simple + present.
例句：If we move the office to the 15th floor, I'll resign.
I'll probably have another panic attack if I see a spider.
第二条件句Second Conditional
意义：用于表达一个假设情况后的结果.
结构：If + subject + simple past, subject + would + verb.
Subject + would + verb + if + subject + simple past.
例句：If I didn't suffer from a fear of flying, I would travel more.
I would consult a doctor if I had a phobia.
第三条件句Third Conditional
意义：是用来表达如果(If)当时那样发生,另外一方面（当时）会如何（通常是指过去的事情,带有一切已经太迟而不能够补救的意思）.
结构：If + subject + past perfect, subject + would have + past perfect.
例句：She was ill. She didn’t go to work.
改成第三条件句：If she hadn't been ill, she would have gone to work.