an

amount用作名词其意为“数量”、“金额”“总额”等，通常用于an amount of，a(great，large)amount of，amounts of这类结构，其后通常接不可数名词。

常见修饰短语

只能修饰可数名词的

a large/great/good number of,a good/great many,dozens of,scores of,quite a few

只能修饰不可数名词的

a great deal of,a large amount of,quite a little,a large sum of

既可修饰可数也可修饰不可数名词的

plenty of,a lot of,lots of,a large quantity of,a good supply of