英文中有3 种语气:直述语气、祈使语气和假设语气。 直述语气用来陈述及询问问题;祈使语气用来指使或恳求他人;假设语气则是用在条件句子中,以表示和事实相反的状态,或者是用在后面紧跟着某些动词类型的子句之中。 例如:
直述语气:The weather is warm．
Is the weather warm?
祈使语气:Let F represent the force in the radial direction．
Note that we neglect the effects of friction．
假设语气:Users require that there be sufficient bandwidth to handle all of the requests．
If I were healthy, I would not need to see a doctor．
需要注意的是,to be 的假设语气,是were 或be,而不是am, is, are 或was。
在科技论文中,有两种情况可能会使用假设语气:(www.xing528.com)
(1)假设语气可以用来表示和事实相反的状态,可以表示可能性,也可以用来提出假设或推测。 例如:
If I were you, I would accept the job offer．(和事实相反)
If the fuel were cleaner, it would burn more efficiently．(假设)
(2)在有些表示请求、要求、建议、命令或期望的动词之后,以that 开头的名词子句中,必须使用假设语气。 此类动词包括ask, command, order, recommend, request, require,stipulate, suggest, wish 等。 例如:
误:We suggest that the user to try to run the program again．
误:We suggest that the user tries to run the program again．
正:We suggest that the user try to run the program again．
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