In linguistics, the lexicon (or wordstock) of a language is its vocabulary, in- cluding its words and expressions. A lexicon is also a synonym of the word thesaurus. More formally, it is a language's inventory of lexemes. Coined in English 1603, the word "lexicon" derives from the Greek λεξικόν
(lexicon), neuter of λεξικός (lexikos), "of or for words", from λέξις (lexis), "speech", "word", and that from λέγω (lego), "to say", "to speak". The lexicon includes the lexemes that together form words. Lexemes are formed according to morpho-syntactic rules and express sememes. The lexicon is generally thought to be a static dictionary rather that a collection
of rules. This dictionary contains both vocabulary organized in one or more ways (all the foods a person knows may be linked in a neural net, for example). The lexicon is also linked to a generative device which combine morphemes ac-
cording to a language's rules. For example, the suffix "-able" can be added to transitive verbs only, so that we get "read-able" but not "cry-able". A lexicon is usually considered to be a container for words belonging to a single language. In other words, multi-lingual speakers are generally thought to have multiple lexicons. Speakers of language variants (Brazilian Portuguese and European Portuguese, for example) may be considered to possess a single lexicon.