Lexicon

In linguistics, the description of a language is split into two parts, the grammar consisting of rules describing correct sentence formation and the lexicon listing words and phrases that can be used in the sentences. The lexicon (or wordstock ) of a language is its vocabulary. Statistically, most lexemes contain a single morpheme. Lexemes composed of multiple morpheme also known as compound words such as idiomatic expressions and colocations are also considered part of the lexicon. In practical applications, such as language learning the lexicon is represented by a dictionary, which lists words alphabetically and provides definition.

More formally, a lexicon is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek ( lexicon), neuter of ( lexikos), "of or for words", from ( lexis), "speech", "word", and that from ( lego), "to say", "to speak".

wikipedia link: Lexicon