The paper describes the process of adapting general Polish lexicon for the purpose of creating legal texts in contemporary Polish. The aim of the article was to completethe existing descriptions of formal mechanisms observed while modifying the original vocabulary. We distinguished and described two basic transformation types: 1) changes in the possible collocations, 2) formal transformations not resulting from a semantic change or being the result of a meaning shift.Compared to the existing analyses, the paper has the advantage of having described transformations not related to meaning changes, which involve 1) replacing an elementof the original expression with a different lexical unit, 2) eliminating parts of the original expression, and 3) completing the original unit with a new lexical element, not existing in dictionaries of general Polish.The paper shows that formal and semantic modifications of general Polish lexicon are an important factor allowing for the enrichment of legal vocabulary. They may also be an obstacle, making it difficult for non-specialists to decode legal texts.