a number of 与several和only a few的区别

a number of 多于several 多于 only a few
大量---一些---很少

the number of ....的数量，跟复数名词时，谓语动词用单数，如：
The number of students is 125.
学生的数量是125人。
a number of 一些，许多，接复数可数名词，谓语动词用复数，如
A number of candidates have been interviewed yesterday.
昨天已经对一些候选人进行了面试。
several用来修饰可数名词，后面用名词复数。这里hundred后面不加s 与several 无关，而是hundred只有在hundreds of 短语中加s，其他指几百时，复数不加s，例如: two hundred, 而不是two hundreds.
few, a few, little, a little
虽然都表示“少”，但
（1）few, a few是可数的, little, a little是不可数的。
（2）a few, a little含肯定意味，few, little含否定意味。这里所谓的“肯定意味”和“否定意味”应该这样来理同样是半杯水，口渴者会认为：There is little water in the glass. 而不口渴的人则会认为：There is a little water in the glass.
一：
1．few修饰可数名词复数。
2．few (= not many; hardly any)含否定意义；a few (= some; several; a small
number of) 含肯定意义。
3． not a few = no few = quite a few = a good few = many。
4． 当 few受 every, last, past, next, some, very等词所修饰时，表示肯定意义，few之前不再有冠词。如：
In the last few minutes, he checked up his paper again.
It took us some few days to repair the machine.
They are very few in number.
There were too few of them.
He goes to see his grandma every few weeks.
5． 在非正式文体中很少见，一般用或代替，如：
Only a few people attended the meeting.
另外，little / a little
Little remains to be done about it. (作主语)
A little remains to be done.
Please give me a little. (作宾语)
He knows a little of everything.
There is very / but little time left. (作定语)
Don’t worry; you still have a little time.
1． little修饰不可数名词，表示“量”。
2． little含否定意义(反义词：much)；a little含肯定意义(反义词：none)。
3． 在非正式英语中，一般很少用little，常用not much, only a little来代替，如：
We haven’t got much money / time.

意思不一样
a number of 很多
several 几个
only a few 只有一点点
都是加可数名词
我觉得就这些.

许多
几个
一点点