Vocab (noun)

A person's stock of words or a specific set of words used in a particular field, profession, or activity.

Origin:

Slang or informal short form of vocabulary.

Examples:

1. He has a great vocab for a kid his age.
2. The vocab of a doctor is different from a lawyer's vocab.
3. The vocab of a musician is different from a businessman's vocab.
4. The vocab of the students was limited.
5. I need to expand my vocab in order to better understand this article.