Vocabulary vs. language

Vocabulary is any word easily spelled and abstractly defined.

Words like egregious and inculcate are vocabulary. Words in a spelling bee are vocabulary.

Language is far more nuanced. Colloquialism, verbiage, slang. The bits and bites of a culture, no matter how small.

Writing with nothing but vocabulary is often so rudimentary it's trite. And prose made of language and nothing else can often be so esoteric it's illegible.

The trick, then, is to write for your users, your customers, and your fans.

To use vocabulary that you and the larger culture understand, but say it in a way that resonates with them and their culture. To write in their language, and in so doing, to strike a chord between what you have to say, and what they want to hear.