插入入就是指插在句子中间，对句子起补充或附加的说明的成分。插入语通常与句中其它成分没有语法上的关系，若将其去掉，句子结构仍然完整。插入语在句中主要起解释、说明、总结等作用，此外还可用于表示说话者的态度和看法、起强调作用、引起别方的注意、转移话题、承上启下等。插入语可能是一个词、一个短语或一个句子。
一、常用做插入语的副词
indeed的确， surely无疑， however然而， obviously显然， frankly坦率地说， naturally自然， luckily (或happily) for sb.算某人幸运， fortunately幸好， strangely奇怪， honestly真的， briefly简单地说等。
eg.
1. Surely, she won't go to China Telecom with you.
当然她不会和你一起去中国电信。
2. Strangely,he has not been to China Unicom. Still more strangely， he has not called me.
奇怪，他未来过中国联通。更奇怪，他没给我打电话。
3. Fortunately,I found the book that I'd lost.
幸亏我找到了已丢失的那本书。
二、常见的作插入语的形容词或其短语
true真的， funny真可笑， strange to say说也奇怪， needless to say不用说， most important of all最为重要， worse still更糟糕的等。
1. Strange to say (或True),he should have done such a thing.
说也奇怪(或真的)，他竟然做出这样的事。
2. Most important of all,you each overfulfiled your own task.
更为重要的，你们各自超额完成了自己的任务。
三、常用作插入语的介词短语
in a few words(或in sum， in short)简而言之， in other words换句话说， in a sense在某种意义上， in general一般说来， in my view在我看来， in his opinion(judgment)按照他的意见(判断)， in conclusion总之， in summary概括地说， in fact事实上， in the first place首先， in addition此外， of course当然， to our knowledge据我们所知， to my joy(delight， satisfaction)使我欣慰(高兴、满意)的， to their surprise(astonishment， amazement)使他们惊奇的， to her regret (disappointment)使她遗憾(失望)的， for instance(或example)例如， as a matter of fact事实上等。
1. Of course， he did not succeed for the lack of experience.
当然，他由于缺乏经验而未成功。
2. She knows much more about computer science than the other students do， for in stance.
例如，她在计算机科学方面就比其他同学懂得多。
四、常用作插入语的分词短语
strictly speaking严格地说， generally speaking一般地说， judging from…根据……判断等。
Judging from his letter， a campaign against "white pollution "has been undertaken in his hometown.
根据他的来信做出判断，一场抵制"白色污染"的运动已经在他的故乡展开了。
注意:不要理解为现在分词短语作状语，因为上两句中speaking和judging的动作不是句中主语发出的。
五、常用作插入语的不定式短语
to be sure无疑地， to sum up概括地说， to tell the truth老实说等。
1.To be sure， community service can aid reemployment.
毫无疑问，社区服务能有助于再就业。
2. To start with， China is ready strengthen scientific and technological cooperation with many countries.
首先，中国准备和许多国家加强科学技术合作。
六、插入句
I am sure我可以肯定地说， I believe我相信，
I wonder我不知道， you know你知道，
you see你明白， that is也就是说，
it seems看来是， as I see it照我看来，
what is important (serious) 重要(严重)的是，
I'm afraid恐怕 it is said据说等。
eg.
1. It will result in success,I suppose.
我想，这件事终于会成功的。
2. One day,it is said， Newton saw an apple fall from a tree.
据说，有一天牛顿见到一个苹果从树上掉下来。
3. What is more important,information superhighways can carry great amounts of information around the country quickly and cheaply.
更重要的是，信息高速公路能把大量信息迅速、便宜地传遍全国。