めもぶろ～目指せペラペラ！～: vocabulary と word

「vocabulary が少ない」「vocabulary を増やさなきゃ」とよく言いますけど、word という言葉もありますよね？vocabulary と word の違いは何だろう？と思って調べてみました。

▶ vocabulary

[LDOCE]
all the words that someone knows or uses
Reading is one of the best ways of improving your vocabulary.
active vocabulary (= the words someone can use)
passive vocabulary (= the words someone can understand, but does not use)

all the words in a particular language
English has the largest vocabulary of any language.

▶ word

[LDOCE]
the smallest unit of language that people can understand if it is said or written on its own
Write an essay of about five hundred words.
I know the tune, but not the words.