Описание тега lexical
The "Lexical" tag is used to denote a connection with words of a language, its grammar or the dictionary. Alternatively, it is also used in the context of "lexical scope," the context in which certain values are valid.
Broadly, Lexical is used to refer to words of a language. (The terms in applicable to natural (human) languages, as well as to computer programming languages. Lexical is derived from "Lexicon" and therefore the tag is also applied to questions relating to the dictionary for a language.
Finally, the tag is used in a computer programming context: Lexical Scoping. A lexical scope is the "context" within with certain rules/values apply (Example the "scope" of a local variable.)