a lot ,可置于句末,意思是很多,通常修饰动词,如：thanks a lot .
词组： a lot of 后接名词,代词,动名词等都可以.还有lots of ,意思差不多,接可数名词,不可数均可.
lot,（指刚提到的数量的）全部,整个儿 You can use the lot to refer to the whole of an amount that you have just mentioned.本条来自金山词典.
希望对你有用.那个用于否定和肯定啊只能说什么反义词之类的啊，不用于否定啊。