关于词汇量与听力的关系，这里还有一个例子可以佐证。

下面是马丁·路德·金的著名演讲 I have a dream 演讲稿片段。

由于面对的听众是受教育程度不高的黑人底层民众，为确保每个人都能够听懂，演讲稿相对比较“平易近人”，但这样的演讲稿仍然出现了不少“超纲词”。

Five score years ago, a great American, in whose symbolic shadow we stand today, signed the Emancipation Proclamation. This momentous decree came as a great beacon light of hope to millions of Negro slaves who had been seared in the flames of withering injustice. It came as a joyous daybreak to end the long night of their captivity.

But one hundred years later, the Negro still is not free. One hundred years later, the life of the Negro is still sadly crippled by the manacles of segregation and the chains of discrimination. One hundred years later, the Negro lives on a lonely island of poverty in the midst of a vast ocean of material prosperity. One hundred years later, the Negro is still languished in the corners of American society and finds himself an exile in his own land. And so we've come here today to dramatize a shameful condition.

上面很多单词词频都落在前10000词以外，如果你的词汇量不过万，那么，你会有很大几率听不懂马丁·路德·金的演讲。

因此，仅仅掌握几千个单词并不足够。

那么，多大的词汇量才算“够用”呢？

下面是词汇量测试网站 http://www.testyourvocab.com 统计出的英语母语人士词汇量分布表：

从上图可见，24岁左右的成年人词汇量均值接近25000。

真正够用的词汇量应该尽可能接近或达到这个值，即2000-25000左右。

当然，词汇积累并不是一件一劳永逸的事情，每个人的词汇量会随着英语学习时间的增加而不断增长，这是一个持续一生的过程。