Abstract: The subject of this research is the concept of definiteness and its lexical-grammatical representation in the scientific discourse of the modern English language. The author notes the universal nature of this concept, since it is a crucial component of communication in any culture, any human society. It was always important for the one who talks and the one who listens to indicate the objects of physical and mental world associated with the world of their things and notions. It is underlined that the development of society and transition from the communal to egocentric perception of the world changed the understanding of the concept of “definiteness”. The novelty of this this research consists in a specific articulation of the scientific problem. The concept of definiteness is viewed within the English scientific discourse, taking into account the crucial facts of lexical-grammatical implementation of this concept in other cognate languages. It is concluded that the changes in the concept of “definiteness” substantiated the peculiarities of the use of positive articles in the modern English-language scientific discourse, and also contributed to the widespread use of the zero article. The methodological framework is comprised of the methods of linguistic research: comparative-historical and comparative analysis; as well as methods of lexical-semantic and syntactic analysis of texts from the English-language scientific discourse.