The article examines the comparison of the lexical meaning of words common for the Kazakh and Uzbek languages. On the eve of the process of transition to Latin (of Kazakh language), it will be important to determine the scientific and methodological basis for the comparative study of related languages. It is important to study the nature of lexical units in neighboring Kazakh-Uzbek languages, the nature of spelling, lexical and grammatical features of the use of oral and written speech. In this work, the analysis of lexical units shows not only a description of individual categories, groups, but also the need to pay attention to the semantic structure of a word, the reasons and patterns of changes in lexical meanings. Revealing the scientific and theoretical foundations and methods of comparative study of lexical units in the Kazakh-Uzbek languages ​​is given priority attention to the study of the historical roots of related languages, identifying similarities in lexical units, analyzing the sound and grammatical features of modern lexical units, determining the scientific and methodological basis of comparative learning. To reveal the topic of the article, the methods of narration, description, comparison, systematization, analysis, generalization, and conclusion are used.