频度副词的概念：
频度副词表示动作发生的次数，常见的有ever, never, rarely, seldom, once, often, occasionally, constantly, frequently, usually, continually, always等。
频度副词的特点：
频度副词表示动作发生的次数，常见有的ever, never, rarely, seldom, once, often, occasionally, constantly, frequently, usually, continually, always等。
频度副词在句中的位置：
频度副词通常位于实义动词之前，动词be、助动词、情态动词之后：
如：He often comes to see us. 他常来看我们。
He is seldom late for school. 他上学很少迟到。
有时为了强调，频度副词也可位于动词be、助动词等之前：
如：She always was late. 她老是迟到。
有的频度副词可位于句末（尤其受very, only修饰时）：
如：I get paid on Fridays usually. 我通常在星期五领工资。
We go out very seldom. 我们绝少外出。
Do you go to the cinema very often? 你常去看电影吗?
有的频度副词（如sometimes, often, usually, frequently, occasionally等）可位于句首（此时多半是因为强调或对比）：
如：Sometimes he went there by bus. 有时他坐公共汽车去那儿。
Very often the phone rings when I'm in the bath. 电话经常在我洗澡时响。
注：含有否定意义的副词置于句首时，其后要用倒装语序：
如：Never have I been there. 我从未去过那儿。
Seldom does he see a film. 他很少看电影。
另外，频度副词always和never通常不位于句首，除非是祈使句：
如：Always remember this. 时刻记住这一点。
Never go out at night. 晚上千万不要出去。
频度副词在否定句中的位置：
在否定句中，有的频度副词可位于否定词not之后或之前（如usually,often），有的频度副词则必须位于否定词之后（如always, constantly, continually, continuously，均含有“连续不断”之意），而有的频度副词却必须要位于否定词not之前（如sometimes, frequently）：
如：He doesn't usually come here./He usually doesn't come here. 他通常不来这儿。
She doesn't always comelate. 她并非总是迟到。(不能说alwaysdoesn’t)
He is sometimes not responsible for what he does. 他有时对他所做的事不负责任。
部分倒装的概念：
倒装英语句子的主语通常位于谓语动词之前，这种语序被称为正常语序。但有时出于修辞或某种特殊的语法结构的需要，需要将谓语动词放在主语之前，这种语序则叫倒装语序。主语和助动词倒置叫部分倒装。
部分倒装：
1、含有否定意义的副词位于句首时的倒装：
在正式文体中，never, seldom, rarely, little, hardly, scarcely, no sooner, no longer, nowhere等含有否定意义的副词若位于句首，则其后要用部分倒装：
如：I shall never forgive him./ Never shall I forgive him. 我永远不会宽恕他。
He seldom goes out for dinner./Seldom does he go out for dinner. 他很少出去吃饭。
She hardly has time to listen to music./Hardly does she have time to listen to music. 他几乎没时间听音乐。
He little realize show important this meetingis./Little does he realize how important this meeting is. 他不甚明白这个会议的重要性。
We had no sooner reached the airport than the plane took off./No sooner had we reached the airport than the plane took off. 我们刚到机场,飞机就起飞了。
注：(1)对于not…until句型，当not until…位于句首时，其后的主句要用倒装语序：
如：He didn't leave the room until the rain stopped./Not until the rain stopped did he leave the room. 雨停了之后他才离开这房间。
(2)某些起副词作用的介词短语，由于含有否定词，若位于句首，其后要用部分倒装：
如：On no accounts must this switch be touched. 这个开关是绝不能触摸的。
In[Under] no circumstances will I lend money to him. 无论如何我也不会再借钱给他了。但是，in no time(立即，马上)位于句首时，其后无需用倒装语序：
如：In no time he worked out the problem. 他马上就算出了那道题。
2、“only+状语”位于句首时的倒装：
当一个状语受副词only的修饰且置于句首时，其后用部分倒装语序：
如：Only then did he realize that he was wrong. 到那时他才意识到他错了。
Only in this way are you able to do it well. 你只有用这种方法才能把它做好。
Only when he returned home did he realize what had happened. 当他回到家里时,才知道出了什么事。
3、“so+形容词或副词”位于句首时的倒装：
副词so后接形容词或副词位于句首时，其后用部分倒装：
如：So cold was the weather that we had to stay at home. 天气太冷，我们只好呆在家里。
So fast does light travel that we can hardly imagine its speed. 光速很快，我们几乎没法像它的速度。
So sudden was the attack that we had no time to escape. 袭击来得非常突然，我们来不及逃跑。
4、“So+助动词+主语”倒装：
当要表示前面提出的某一肯定的情况也同样适合于后者，通常就要用“So+助动词+主语”这种倒装结构：
如：You are young and so am I. 你年轻，我也年轻。
She likes music and so do I. 她喜欢音乐，我也喜欢。
If he can do it, so can I. 要是他能做此事，我也能。
注：(1)若前面提出某一否定的情况，要表示后者也属于同样的否定情况，则应将其中的so改为neither或nor：
如：You aren't young and neither am I. 你不年轻，我也不年轻。
She hasn't read it and nor have I. 她没有读它，我也没有读。
(2)注意该结构与表示强调或同意的“so+主语+特殊动词”结构的区别：
如："It was cold yesterday." "So it was."“昨天很冷。”“的确很冷。”
"Father, you promised." "Well, so I did."“爸爸，你答应过的。”“嗯，是答应过。”
5、由not only…but also引出的倒装：
当not only…but also位于句首引出句子时，not only后的句子通常用部分倒装形式：
如：Not only is he a teacher, but he is also a poet. 他不仅是一位教师，而且是一位诗人。
Not only did he speak more correctly, but he spoke more easily. 不仅他讲得更正确，也讲得更不费劲了。
6、虚拟条件句省略if后构成的倒装：
当if引导的虚拟条件从句中含有had, were, should等时，如将if省略，则要将had, were, should等移到主语前，构成倒装句：
如：Had you come yesterday, you would have seen him. 若你昨天来，你就会见到他了。
Should you require anything give me a ring. 如果需要什么，可以给我打电话。
Were it not for your help, I would still be homeless. 要不是你帮助，我会仍然无家可归。
注：省略if后提前的had不一定是助动词：
如：Had I money, I would buy it. 假若我有钱，我就会买它。