The research is devoted to the history of the formation of the concept of “Azerbaijani language” and aims to identify the stages of “clarification” of the concept, which covers a period of about a thousand years. Research shows that the concept of “Azerbaijani language” directly depends on the degree of differential perception of this reality, in other words, its cognitive nature, because it reflects the reality of the specific ethnic (national) language expressed by it. Therefore, throughout the study, the language reality of the concept of “Azerbaijani language” at different historical stages (with socio-cultural, structural and literary-normative features) and how to express this concept, i.e. with what linguonyms (for example, “Turkish language” or “toponym + Turkish language” or “Azerbaijani language”) is studied in interaction. And in this case, the positions of both “internal”, i.e. native speakers, and “foreign”, i.e. authors from other nations (for example, Arab, Persian, Russian, other Turkic peoples) are taken into account. The first aspect that determines the relevance of the topic is that a number of scientific and socio-political sources are skeptical of the linguonym “Azerbaijani language” and support the idea of calling it “Azerbaijani Turkish” or even “Azerbaijani (Azeri) dialect of Turkish”.Keywords: Azerbaijani Turkish, linguonym, concept, Turkology, dialect.