The total stock of words in a language. The lexis of the English language is vast and constantly evolving.
The vocabulary of a person, language, or branch of knowledge. Medical lexis can be difficult to understand for those outside the profession.
The choice of words or diction used in a particular piece of writing or speech; style. The novelist's lyrical lexis gives the narrative a poetic quality.
The branch of linguistics that studies the vocabulary of a language (lexicology). Lexis focuses on how words combine and develop meaning within a corpus.