The article introduces an attempt to establish suitable principles of defi ning subject as one of the main parts of sentence for ergative languages of Dagestan. The problems of syntactic division of sentence and peculiarities of its members in Dagestani languages are still examined only in general. Even the question of the number of principal sentence members is still under discussion. Only semantic or pure formal features are traditionally used as the criteria for distinguishing between sentence members. Within Dagestani languages studies there are no special researches devoted to this question. To distinguish the predicative of sentence the authors suggest using three levels of the language: syntactical, semantic and pragmatic ones. However, the article gives priority to syntactical features as members of the sentence are syntactical category, and their specifi cs should be found in peculiarities of combination of words while forming a sentence. Formal criteria are also very important, but apart from morphology, syntax is interested not in forms of words separately but in their combination with each other. In some sentence constructions it is exactly the word order that is the only criteria of the subject as a principle member of sentence. Subject as syntactic element is characterized by defi nite relationships with other parts of sentence; therefore word order is suggested to be the fi rst identifi ed feature of subject which holds the fi rst left position in a sentence. In every language there are some means which express syntactical connections between words within a sentence, which help ‘recognize’ members of sentence. These are morphological (structural), semantic and syntactical means. In ergative languages these means play different roles for different structures of sentence. For absolute sentence constructions, morphological means of expressing connections between words in a sentence are rather important. Correlation is a morphological means of connection, as it is used through forms of words. For ergative sentence constructions, semantic means of expressing syntactical connections are also very important. In this case, the semantic factor is the key one in defi ning members of sentence. Subject in this case is defi ned by means of comparison of semantic contents of the sentence (only its meaning), as functional homonymy of ergative and absolutive cases prevents distinguishing between subject and object of sentence. As for ergativoid (bi-absolutive) constructions, their criterion is a pure syntactical means of expressing syntactical connections, i.e. the word order. For other types of constructions word order is not the main criteria for distinguishing members of sentence, however, any change of word order infl uences the meaning of the sentence. In ergative and absolutive constructions syntactical connections and functions of certain words during the change of word order, in contrast to ergativoid construction, do not change but the sentence as a whole obtains a rather new shade of meaning. Thus, the word order in Dagestani ergative languages plays a very important role for the structure and contents of sentence.