It is emphasized in the article that in order to understand various texts correctly, it is necessary to know a certain quantity of words and the main grammar rules and to have the skills necessary to process the information conveyed in a meaningful text. The research carried out by linguists and methodologists has demonstrated that neither secondary, nor higher non-philological school teaches the necessary lexis amount. According to the author, this problem may be solved by formation of the potential vocabulary. There are both linguistic and methodical presumptions, like: linguistic-formation of words, and methodical-transformation of unknown words into equivalent word combinations and analysis of the word formation. This article may be useful for lecturers-practitioners and methodologists-theoreticians.