语法是英语学习的基础，也是的基础，掌握好英语语法无论是对还是以后的英语学习都是有很大帮助的。下面频道为大家整理了常考知识讲解，一起来学习一下吧!
　　英语常考知识点讲解：only
　　一、only引导的词组或句子放在句首作状语时，通常要用倒装结构。
　　如 only in this way can you solve the problem. 只有通过这种方式你才能解决问题。 only if you study hard can you pass the exam. 只有努力学习才能通过考试。 only then did I realize my mistake. 只有那时我才意识到错了。
　　二、not only...(but also)出现在句首时，如果架连接的是两个句子，常用倒装。
　　如 Not only did we lose all our money,but we also came close to losing our lives. 我们不仅丢了钱，还差点把命丢了。 Not only did he speak correctly,but he also spoke easily. 他不仅说得准确，而且说得很轻松。
　　三、only放在不定式前面，常表示不愉快或出乎人们的意料的结果。
　　如 I went all the way to his home only to find hime out at a meeting. 我径直到他家里去，不料发现他出去开会了。 I hurried to the post office only to find it closed. 我匆忙赶到邮局，不料已经关门了。 She went home only to find her house burglarized. 她回到家里，发现房子被盗了。
　　四、“too...to...”结构中，表示否定意思，但在“only too...to...”结构中，only too = very，表示肯定意思。
　　如 The patient is too weak to walk. 那个病人太虚弱了，走不动。 We are only too willing to do it for you. 我们非常愿意为你做那事。 I am only too delighted to accept your king invitation. 我非常高兴地接受你的邀请。
　　五、在“one of 复数名词 定语从句”的结构中，定语从句一般被看作修饰复数名词，谓语要用复数形式。但在“the only one of 复数名词 定语从句”的结构中，定语从句却被看作修饰“the only one”，谓语动词要用单数形式。
　　如 This is one of the best novels that have been published in the past two years. 这是近两年出版的比较好的小说之一。 He was the only one of the boys who was given a prize. 他是这些孩子中受到奖励的。 She is the only one of the girls who has been to the US. 她是那些女孩中仅有的去过美国的。
　　六、If only 为虚拟语气的一种，表示愿望或一个未实现的条件，多用于感叹句，其主句常常省略。
　　如 If only she would marry me! 她要是能和我结婚该多好! If only he had known about it! 他那时要是知道这件事该多好! If only you could have been here earlier that day! 要是你那天再早点到这就好了。 If only there were forty-eighty hours in a day. 要是一天有48个小时就好了。