a great many后直接接复数名词，动词用复数。用于肯定句中，相当于many，a large number of。many既是限定词，用于修饰名词，也是不定代词，代替名词。在many farmers中，many是限定词；在many of短语中many是代词。
A great many和 a great many of的区别
一、a great many后直接修饰名词,名词可以有修饰语,如:
a great many students
a great many young students
二、a great many of后主要接：
1.代词：a great many of them
2.受冠词修饰的名词：a great many of the students
3.受these,those修饰的名词：a great many of these students
4.受物主代词修饰的名词：a great many of my students
5.受所有格修饰的名词：a great many of Tom’s students