lexis

Lexis is a term used in linguistics to denote the vocabulary of a language—the set of words and fixed expressions that speakers recognize and use. It encompasses not only single words but also multiword units, collocations, idioms, and other lexical items that carry meaning beyond individual morphemes. Lexis is often contrasted with grammar, which governs rules for combining elements; lexis refers to the inventory of lexical items and their semantic relationships. In corpus and functional linguistics, lexis is studied to understand lexical density, frequency, collocation patterns, and semantic fields.

In lexicography and language pedagogy, lexis is central to how languages are learned and described. The term emphasizes vocabulary knowledge over morphology or syntax alone. Lexical items may be recorded in a lexicon or dictionary, while phraseology highlights fixed or semi-fixed expressions and collocations that users rely on for fluent speech. The lexical approach to language teaching focuses on acquiring a broad, usable vocabulary, including chunks of language.

The Lexis diagram is a graphical tool in demography and epidemiology named after Wilhelm Lexis. It plots age on one axis and calendar time on the other, with diagonal lines representing birth cohorts. This representation allows analysts to examine how risk, incidence, or mortality vary by age and period and to disentangle cohort effects. The concept is widely used for studying population health and social trends.