Definition of a "lexicon" in Named Entity Recognition I am writing a paper on Named Entity Recognition and I mention that in the literature were proposed a lot of methods which make use of lexicons. However, I am struggling to find a definition of a "lexicon" which I can cite. As far as I understand, a lexicon is a list of lemmatas (word parts), whole words or word combinations where these are classified to an entity. So, for example if in a sentence i have "New York is located in" and in my lexicon I have the pattern " X is a located in" -> CITY my system will look up the pattern and see that New York belongs to the entity CITY. 
Could someone explain to me if I am wrong? If so, I would like to get a definition of a "lexicon", "gazzetteer" and "dictionary", because I get the feeling that some of these are sometimes used interchangeably in papers.
As far as I know the word "lexicon" is mostly used for a simple list of words (or terms), I would say it's quite rare to use it for describing a list of patterns/rules. "gazetteer" and "dictionary" would be a bit more general in my opinion, for instance one can have a "dictionary of rules" which associates specific patterns with actions. But overall I agree with your impression that these terms are often used interchangeably, I'm not aware of any standard definition.