vocabulary 作“词汇”解，指“所认识的单词总数”（词汇量）或指“所用的单词的总数 ”（词汇表），是集合名词，不用复数形式，不可用来指一个具体的单词。word 则指一个一个具体的单词，是可数名词。例如：

1. 不可说 You've missed out one vocabulary. 应该说You've missed out one word.  

2. 不可说 He has a great number of vocabularies. 而应该说He has a large vocabulary. 或 He possesses a wide vocabulary of English words.

3. “单词记得多”可以说have a large / rich / wide vocabulary;

4. “单词记得少”可以说 have a small / poor / meagre vocabulary, 不可说have many vocabularies 等。