Language acquisition means the development of language abilities. First language, the native one, we usually acquire from the environment, spontaneously. Human brain possesses an innate mechanism ready to be activated when as a child we reach a certain stage of development. It is followed by understanding and the use of the speech. In the first year of life, child already understands certain rules of its language, and in third the basic structure of speech that it overhears from the vicinity. The purpose of this work is to inquire examine different aspects which denote and influence on adoption of native language and the speech development. At the beginning of the research examinee was three years and six months old. Spontaneous speech was recorded during the period of eight months with analysis of morphological characteristics of that speech. Additionally, objects of research were speech syntax trough sentences by composition and observation of length development of examinee's statements. Finally, the speech complexity was as well examined with lexical density and lexical diversity. Collected results show that a preschool child, coming from stokavian dialect and ikavian local population's speech, uses specific morphological forms compared with standard language. Also, it uses some inventive lexem sand adopts some morphological forms from the surroundings. As regards to syntax the child mostly used simple extended sentences while speaking. Towards the end of the observation the use of complex sentences notably increased, especially the use of multiple complex sentences. In terms of complexity of the speech, lexical density is average value and lexical diversity lower value. It should be pointed out that common use of certain words indicates their good adoption.