The object of the research is the definition of forgery as it is used by the legislation, in particular, in Article 326 of the Criminal Code of the Russian Federation. The authors see the following problems: no legal definition, no single point of view in the doctrine of criminal law and incoordinations with other terms used in law. The wording 'forgery or counterfeiting state registration sign' used in Article 326 of the Criminal Code of the Russian Federation makes the situation even more complicated. Thus, the subject of this research is different doctrinal interpretations of the term 'forgery' and judicial practice. The methodological framework of the research covers such methods as analysis and synthesis, comparative law analysis, system-structured and formal law approaches, theoretical prognistic method and interpretation of legal provisions. The novelty of the research is caused by the fact that the author offer their own definition of the term 'forgery' and concludes that forgery and forgery documents/items are compatible and intersecting terms. The authors also conclude what criteria of truth and authenticity can be used to describe items/documents as forgery-counterfeiting, forgery but not counterfeiting and counterfeiting but not forgery. They also make recommendations on what amendments should be made in the applicable law.