One of the prior conditions for Turkish to be used effectively and efficiently in written expression is that a language has rich vocabulary. The aim of this study is to put forth the relationship between different variants and active use of words in the 6th grade students in the primary education. It is also aimed to lead the work of teaching Turkish as mother tongue. In this study, first and foremost, the past and current situation of teaching vocabulary is to be dealt with. Furthermore, the issue of teaching Turkish vocabulary will be discussed. Before teaching vocabulary in mother tongue in class, a student’s active vocabulary is to be determined, and the content of the vocabulary education is to be shaped according to the data obtained from this study. In this research, a qualitative study has been used, and this research has been designed as a case study. The target group of the research consists of 37, sixth-grade primary school students, whose parents have declared personal information in forms, two written expression papers per student and also researcher’s observation notes have been analysed.The data obtained from the research are interpreted under these categories: 1. A total number of words used in the written expression of students, 2. The average number of words used by each participant, 3.the number of the words most frequently used, 4. The number of the words used by boys and girls, 5. Numbers for the parts of speech in use. Moreover, the issues related to the educational and income status of parents, whether the mother works or not and the number of siblings are compared with the data obtained.Keywords: Vocabulary, Teaching Turkish Vocabulary as Mother Tongue, Written Expression