爱华网Only作形容词
意为：惟一的，仅有的；(子、女)独生的；最好的；最合适的，独一无二的。
【例句】John is the only person who can read my mind. 约翰是惟一真正看透我心事的人。
【真题】There was never any time for Kate to feel lonely, ____ she was an only child. (2005辽宁)
A. ever since B. now that
C. even though D. even as
【解析】Only child的意思是独生子/女，了解了这一点，可以推断出主从句之间为让步关系，选择C项。全句的意思是：尽管凯特是独生女, 但她在任何时候都从未感到过孤独。
Only作副词
⒈ 常见的意思是“仅仅，才”，常位于所修饰的动词、短语或从句前，如：
【例句】At present we can only wait and see.
目前我们只好等一等看。
此时，only若放在句首修饰作状语的形容词、副词、介词短语或状语从句等，主句要采用部分倒装，如：
【例句】Only when she was at an impasse (n. 绝境), did she feel great pleasure in doing so.
只有当她陷入绝境时，她才乐意这么做。
Only at home, does my uncle say I am able.
只有在家，我叔叔说我很能干。
Only in Paris do you find bars like this.
Only if these conditions are fulfilled can the application proceed to the next stage.
In formal written English only, or only if and its clause, can be placed first in the sentence. In the second part of the sentence, be , do , have, etc. come before the subject and the main part of the verb
需要注意的是，如果置于句首的“only + 状语”结构是强调句,It is (was)...that...中被强调的对象，则主句不倒装。
【例题】It was only when he was in trouble _____ the value of our help.
A. that did he realize B. did he realize
C. did that he realize D. that he realized
【解析】此例句是含有“only+状语从句”的强调句型, 强调的正是时间状语从句，句子用正常语序，正确答案是D项。
⒉ 另外，only作副词时，还有“不料；结果却”这个意思。此时，only常和不定式连用，作结果状语，表示出乎意料或令人失望的结果。当”only+不定式”结构引导结果状语从句时，表示结果的事件紧接前述事件发生。
【例句】He hurried home only to find the guests had left.他匆匆忙忙赶回家, 结果发现客人们已经走了。
【例题】He got to the airport _____ to find that the plane had left two minutes before.
A. just B. only C. in order D. almost
【解析】Only + 不定式结构表示令人失望的结果。题干句意为：他到达机场，结果发现飞机在两分钟之前飞走了。正确答案为B项。
【真题】It took her nearly half a year to find his address, only learning that he had passed away ten years before.(1994上海，改错题)
【解析】这里需要注意的是only与-ing形式连用也可用于表示结果，意为“结果只是……”，only起强调作用，如：He died only leaving debts. (他死后只留下一身债。) 但是only与不定式结构连用作结果状语，表示意想不到或令人失望的结果。可以看出，句中的结果是令人失望的。因此，“only learning”应改为“only to learn”。
由Only构成的习惯搭配
⒈ Not only...but also...作为连词，连接两个并列成分。当连接两个并列句时， not only 所在的句子要采用部分倒装，but also 后面的句子用正常语序，可以巧记为：前倒后不倒。
【真题】_____ snacks and drinks, but they also brought cards for entertainment when they had a picnic in the forest.(2004上海)
A. Not only they bought
B. Not only did they bring
C. Not only brought they
D. Not only they did bring
【解析】综上所述， not only后面的分句部分倒装。因此, 正确答案是B项。
注意：Not only... but also...与主谓一致关系??Not only...but also...作为连词，还可以连接并列的主语、谓语、宾语等，连接主语部分或者谓语部分时，要注意保持主谓一致。Not only...but also...连接主语时，如同or、either...or...和neither...nor...，谓语动词的数服从就近原则??最靠近谓语动词的主语部分决定谓语动词的单复数。
【真题】Not only I but also Jane and Mary ____tired of having one examination after another. (1989全国)
A. is B. are C. am D. be
【解析】 句中not only...but also...连接并列主语I和Jane and Mary，根据就近原则，因为Jane and Mary为复数概念，谓语动词用复数形式。因此，正确答案是B项。
【真题】Playing football not only makes us grow up tall and strong but also give us a sense of fair play and team spirit. (1998全国，改错题)
【解析】句中的主语是“playing football”，“make”和“give”是由not only...but also...连接的并列谓语动词，根据主谓一致原则，都用单数形式。因此，“give”应改为“gives”。
⒉ 从属连词If only表示不能实现或难以实现的意愿或愿望，意思为：要是……该有多好啊！引导的句子相当于感叹句，多用虚拟语气。
表示与现在事实相反的假设，用一般过去时，如：
【例句】If only I were beautiful as you are.
我要是和你一样漂亮就好了。
表示与过去事实相反的假设，用过去完成时，如：
【真题】Look at the trouble I am in! If only I ____ your advice.(2003上海春)
A. followed B. would follow
C. had followed D. should follow
【解析】If only所在的句子表示与过去事实相反的假设，正确答案为C项。
表示与将来事实相反的假设，用would +动词原型，如：
【例句】If only he would reply to my letter.
要是他能给我回信就好了！
虽然If only大都用在虚拟条件句中，但是也可用于真实条件句中，如：
【例句】 If only he would get the job, it would make a great deal of difference.
他要是能得到这个工作，情况就会大不相同。
⒊ Only if是由充当前置修饰语的副词only和从属连词if组合而成的，表示惟一条件，意为“只有……才……”，引导让步状语从句，用以表示条件。Only if易与if only混淆，这一点要特别注意。
【例句】Will you come? 你来吗？
Only if you promise not to invite Mary.只要你保证不请玛丽(我就来)。
Only if these conditions are fulfilled can the application proceed to the next stage.
