含义和用法上，a great number of 与 a great many of 有着细微的区别。
a great number of 用来形容大量的可数名词复数，它强调的是数量多，类似于 plenty of 或 a lot of 的用法。比如："A great number of water fowls dwell on the island." 这句话意指岛上栖息着许多水鸟。
而 a great many of 则强调的是某一范围内的很大一部分。它表示的是比例，类似于 a large part of。例如："A great many people are often willing to sacrifice higher pay for the privilege of becoming white collar workers." 这句话的意思是，许多人常常愿意牺牲较高的薪水，以换取成为白领工人的社会地位。
进一步来看，"A great many of them are graduates of special training schools for die-hards." 这句话中的 a great many of 强调的是顽固分子中很大一部分人拥有特殊培训学校的背景。
最后，"Now a great many of them are out of work." 说明失业的人群中很大一部分人面临就业困难。
而在财政补贴方面，"Total agricultural subsidies in 2009 were around $16 billion, which would pay for a great many of the ideas that follow." 表示2009年的农业补贴总额约为160亿，足以支持许多后续的想法实施。
