什么时候主语后直接加比较级 例：So it's bigger and busier than Cambridge.

比较是人们认识客观事物的一种重要手段,正可谓“有比较才有鉴别”.在英语中,人们常用“more(...) than...”结构比较人和事物之间存在的某种差异,“more(...) than...”表示“比……多……”或“比……更……”的意思,“than”用作连词,引导比较状语从句.这是 “more(...) than...”结构最基本的意思.例如：
1.His speech was more interesting than I had expected (it would be).他的演讲比我预想的有趣.
2.He considered her opinions were more valuable than ours (our opinions were).他认为她的观点比我们的更有价值.
但“more(...) than...”结构除了最基本的比较意义之外,还有一些其他的用法,“than”的词性发生了变化,其后的成分也有所变化,英语学习者应在使用中留意这些变化.
1．“A + be +形容词比较级 + than + B” 意思为“A比B更……”.
如：This tree is taller than that one.这棵树比那棵树高.
注意：
① 在含有连词than的比较级中,前后的比较对象必须是同一范畴,即同类事物之间的比较.
②在比较级前面使用much,表示程度程度“强得多”.
如：A watermelon is much bigger than an apple.
③ very,quite一般只能修饰原级,不能修饰比较级.
2．“比较级 + and + 比较级”或“more and more +原级”表示“越来越……”
如：It becomes warmer and warmer when spring comes.
春天来了,天气变得越来越暖和了.
It is getting cooler and cooler.
天气越来越凉爽.
The wind became more and more heavily.
风变得越来越大.
Our school is becoming more and more beautiful.
我们的学校变得越来越美丽.
3．在含有or的选择疑问句中,如果有两者供选择,前面的形容词要用比较级形式.
如：Who is taller,Tim or Tom?谁更高,Tim还是Tom?
4.“the +比较级……,the+比较级”,表示“越……越……”.
The more money you make,the more you spend.
钱你赚得越多,花得越多.
The sooner,the better.
越快越好.
5.表示倍数的比较级用法：
①.A is …times the size /height/length/width of B.
如：The new building is three times the height of the old one.
这座新楼比那座旧楼高三倍.(新楼是旧楼的四倍高)
②.A is …times as big /high/long/wide/large as B.
如：Asia is four times as large as Europe.
亚洲是欧洲的四倍大.(亚洲比欧洲大三倍)
③.A is …times larger /higher/longer/wider than B.
如：Our school is twice bigger than yours.
我们学校比你们学校大两倍.
6.形容词、副词的最高级形式主要用来表示三者或三者以上人或事物的比较,表示“最……”的意思.
句子中有表示范围的词或短语.如：of the three,in our class等等.
如：He is the tallest in our class.
他在我们班里是最高的.
7."否定词语+比较级","否定词语+ so… as"结构表示最高级含义.
Nothing is so easy as this.
=Nothing is easier than this.
=This is the easiest thing.
8.比较级与最高级的转换：
Mike is the most intelligent in his class.
Mike is more intelligent than any other student in his class
7.修饰比较级和最高级的词
1）可修饰比较级的词
①.a bit,a little,rather,much,far,by far,many,a lot,lots,a great deal,any,still,even等.
②.还可以用表示倍数的词或度量名词作修饰语.
③.以上词(除by far)外,必须置于比较级形容词或副词的前面.
注意：使用最高级要注意将主语包括在比较范围内.
(错) Tom is the tallest of his three brothers.
(对) Tom is the tallest of the three brothers.
2)下列词可修饰最高级：by far,far,much,mostly,almost.
This hat is nearly / almost the biggest.
注意：
a.very可修饰最高级,但位置与much不同.
This is the very best.
This is much the best.
b.序数词通常只修饰最高级.
Africa is the second largest continent.
8.要避免重复使用比较级.
(错) He is more cleverer than his brother.
(对) He is more clever than his brother.
(对) He is cleverer than his brother.
9.要避免将主语含在比较对象中.
(错) China is larger that any country in Asia.
(对) China is larger than any other country in Asia.
10.要注意对应句型,遵循前后一致的原则.
The population of Shanghai is larger than that of Beijing.
It is easier to make a plan than to carry it out.
11.要注意冠词的使用,后有名词的时候,前面才有可能有名词.
比较：Which is larger,Canada or Australia?
Which is the larger country,Canada or Australia?
She is taller than her two sisters.
She is the taller of the two sisters.
10.连用词
much ,a little ,a bit,even

其实这两种形式是一样的，都是在系词is后的比较级形式。只不过比较级的形式组成不一样，第一个是形容词后可以直接加er的，再一个就是形容词前加more，这是两种比较级的组成形式。仔细想想

这是对词而言的，它们都是直接加比较级，只是词的比较级不同，像第一个句子
big的比较级是bigger ，busy的比较级是busier
，第二个句子 tiring的比较级就是more tiring
词的比较级都是要背的
一般长音节词的比较级都是more+本身

1、单音节词或少数双音节词的比较级是词尾加+er，就是你说的主语后直接加比较级的意思。
例如bigger、faster之类的
另外还有不规则的比较级形式也是主语后直接加比较级：例如better之类的。
2、两个或两个以上音节的词的比较级：词前+ more,即是你说的加more...than的。例如：tiring,quickly之类的。...