1. 用于 a lot of (=lots of)，意为“许多”，可用于修饰可数或不可数名词。如：
We need a lot of [lots of] money. 我们需要很多钱。
He has quite a lot of [lots of] friends. 他有很多朋友。
修饰主语时，谓语的数取决于它所修饰名词的数。如：
A lot of money was spent on it. 在它上面花了很多钱。
A lot of people were interested in it. 对此感兴趣的人很多。
2. 单独用的a lot具有以下用法：
(1) 用作主语。如：
A lot hangs on this decision. 很多事情都取决于这一决定。
A lot will depend on how she responds to the challenge. 在很大程度上将取决于她对这一难题的反应。
(2) 用作宾语。可用动词宾语或介词宾语。如：
Sophia must have been through a lot. 索菲娅一定受过很多苦。
I have learned a lot from him since I have known him. 自从我认识了他，我向他学到许多东西。
(3) 用作表语。如：
Two hundred pounds is a lot to spend on a dress. 买一件衣服要花200英镑是够多的。
(4) 用作状语。一是用于修饰比较级，二是用于修饰动词：
①修饰比较级，相当于much，意为“……得多”。如：
It’s a lot colder today than it was yesterday. 今天比昨天冷得多。
Houses are a lot more expensive these days. 如今的房价贵多了。
②修饰动词，一是表示程度，意为“很”“很多”“非常”等；二是表示频率，意为“经常”。如：
He has helped me a lot. 他给予了我很大的帮助。
George smokes a lot. 乔治烟抽得很多。
I play tennis quite a lot in the summer. 夏天我经常打网球。
She is very pretty and goes out a lot. 她长得很漂亮，常常到外头玩。
在口语中，有时可用lots代替a lot。如：
She loves him lots. 她非常爱他。
There’s lots we can do. 有许多事情我们可以做。
I eat lots less than I used to. 我吃得比从前少得多。