The article considers one of the most difficult problems in the spelling of the In the spelling of the Kazakh language is the search for reasons for joint or separate spelling of words. According to this, Kazakh linguistics was conducted a review research, and studied the recognition of a joint word in morphology, semasiology, and spelling. Beginning with the research of A. Baitursynov and K. Zhubanov, a review of the works of scientists who became the subject of a special study of this topic was conducted. Some of the authors’conclusions are distributed and differentiated. Phonetic reasons and signs of merging complex words: Professor K. Zhubanov, semantic sign defended his thesis on this topic. As noted by academician R. Syzdyk and professors N. Uali, B. Kaliev for the first time studied and published in scientific circulation, and in particular, in the joint construction used the connotation-denotation theory of profesor N. Uali, on this basis they made a scientific conclusion