比较
1，比较级必须要有than;compared with/to, in comparison to, as compared with，不能和表示比较的词连用
2，于是我们发现，"double"后面往往跟这一类的词：amount, quantity, speed, frequency, rate (of), rates (for), price, ...有规律吧?肯定不能跟"apples""students"这一类的具体的东东。归纳一下, “a doubling of” 后面跟什么样的词?
数量(number,amount, quantity…)，价值，一些物理量(如concentration, pressure, force…)
Increase是一个事物自身前后的比较，所以做名词时一定要判断increase所指代的内容到底是什么。自身是否可数要看Increase所指代的内容来决定
3，twice和double的用法
(1)twice，double和as...as也可以做同位语修饰，要紧接其修饰的内容，必须是figure,number一类的名词(如：.........A，twice/times/double (as.....as).......
(2)twice as many as 可数名词。Twice as much as不可数名词。如果noun is already an explicitly numerical quantity, you should just use "twice" or "double" by itself.
e.g., twice the increase --> "increase" is an explicitly numerical quantity
(3)倍数表达
1.“A be 倍数 as 计量形容词原级 as B”。
This tree is three times as tall as that one.
这棵树是那棵树的三倍高。
2.“A be 倍数 计量形容词比较级 than B”
The Yangtze River is almost twice longer than the Pearl River.
长江差不多比珠江长两倍。
3.“A be 倍数 the 计量名词 of B”
The newly broadened square is four times the size of the previous one.
新扩建的广场是未扩建时的四倍大。
4.“The 计量名词 of A be 倍数 that of B”
The size of the newly broadened square is four times that of the previous one.
新扩建的广场为以前的四倍大。
5.x times + what 分句 (名词性从句相当于名词)
6.x-fold
三类表示倍数的形容词为：twofold, threefold, fourfold, tenfold等。以twofold为例，其意思为two times as much or as many of something。该类词为形容词，多用于构成形容词+名词的词组，如：a threefold increase in revenue，少用于比较两个事物之间的倍数关系。
4，times as much + subject + verb. + prep. phrase + as + (subject + verb.) + prep. phrase固定比较结构。
At least as....as...=as...as...or more...than(>=)at least or more必错!!
sb. be + 百分数 + more/less likely than sb to do sth.(前面的to do 能省，后面的不能省)
如：at least fifty percent less likely than those who are sedentary to die of a heart attack
1. 比较结构as adj. a noun. as... ：
as....as之间是可以加 adj+noun的，不过好像只限于几种形式(张振邦)：
as+adj.+不定冠词+单数可数+as I haven't seen as old a car as this for years.
as+adj.+零冠词+不可数名词+as 对应 prep2-9 (见类似题链接)
as+adj.+零冠词+复数可数名词+as I don't smoke as expenesive cigarettes as those.
2. as adj. (a) noun. as = (a) noun. as adj. as，其中第一个as是adv.
5，
(1) whereas连接的平行比较只要求对比的核心逻辑上有对称关系，不要求对称位置必须是对称名词，下面句子中主从句的主语分别是energy和nuclear power并不是对称名词，但是对比的核心都是“核能发电占总产出能量的份额”：
如OG12-131 Over 75 percent of the energy produced in France derives from nuclear power, whereas nuclear power accounts for just over 33 percent of the energy produced in Germany.
*：但是如果whereas后面接介词短语，那么主句的开头也必须需要是介词短语(whereas后出现介词短语或者状语都会非常对称)，如果whereas后接单纯主谓宾(或主系表)，主句也要尽量用单纯的主谓宾(或主系表)来对应，除非同下面GWD 18-2一样后半句主谓即已经可完全表达出“对称”的含义(each language occupies a distinct area of the brain是主谓宾齐全;language areas overlap是主谓，没有宾语。但两个分句依然算是平行，因为逻辑已经平行。)：
prep1-54 In cooking, small quantities of spices are used, whereas in medicinal usage spices are taken in large quantities in order to treat particular maladies.
(2) like/unlike是严格的硬梆梆比较，比较对象必须严格对等，中间尽量不能插入任何成分(比如有一个题目是:Unlike A, in 1990 B...就算A，B可比，但这样就是不佳的表达，因为这会让读者花费脑细胞去找unlike和哪个在比。最好的句子一定是排版最严谨、最遵循规则的句子，一定是读起来最省力的句子)，但是非限制性定语从句这一类非常明确是紧跟着前面的名词的修饰成分是可以的。Similar=like，different from=unlike，但是similar to和different from一般不可放在句首
6，
1) compared with直接跟在逗号后面可以修饰逗号前面名词短语的核心词：
Example：
In the United States, while the number of foreign-born residents and their children is higher than ever, the percentage of the population they represent is not; in 1910 this group made up 35 percent of the population, compared with 20 percent in 2000.
2) Compared with也可以修饰前面整个分句，compared with后面的名词与主语比较：
Example:
u Today, more than 43 percent of Californians under the age of eighteen are Hispanic, compared with about 35 percent a decade ago.
u In the United States, Fifty-two percent of high school graduates go on to college, compared with thirty-five percent in Canada and fifteen percent in Great Britain, Japan, and West Germany.
u One baby in four is now born to a mother aged thirty or older, compared with just one in six in 1975.
3) as compared to/with中as指代前面整句的核心含义：
A recent review of pay scales indicates that, on average, CEO's now earn 419 times the pay of blue-collar workers, as compared to 42 times their pay, the ratio in 1980.
4)注意contrary to放在句首,后面必须加上idea, belief等抽象名词修饰主句,不存在比较双方的问题.
5)Compare不能使用主动形式!!必须使用被动形式
例: Contrary to popular belief, victors in the ancient Greek Olympic Games received cash prizes in addition to their laurel wreaths.