a lot of、lots of、a number of( /large numbers of)、a great deal of、plenty of的区别：五个“名词+介词”短语都表示“大量,许多”。
a lot of(或lots of)既可以修饰不可数名词也可以修饰可数名词的复数形式,可以相应地换为much和many;
plenty of“足够、大量”,既可以修饰不可数名词也可以修饰可数名词的复数形式。
a number of / large numbers of只可以修饰可数名词复数形式(它修饰的词作主语时谓语用复数形式)可以换为some、many、a lot of、plenty of。
a great deal of只可以修饰不可数名词(它修饰的词作主语时谓语用单数形式)可以换为much。
A lot of people think that time is money.
(许多的人认为时间就是金钱。)
I don’t have to do it in a hurry because I have plenty of time.(我用不着赶忙,因为我有充足的时间。)
I have a number of letters to write today.
(今天我有好多信要写)
I spend a great deal of time/money on shopping.
(在购物方面我花费了大量的时间/金钱。)