Somaye Rajabzade - Department of Education and Psychology, Payame Noor University,Tehran ,Iran
Mahmoud Ekrami - Department of Education and Psychology, Payame Noor University,Tehran ,Iran
Faramarz Soheili - Department of information science, Payame Noor University, Tehran ,Iran
Hamid Maleki - Department of Education and Psychology, Payame Noor University,Tehran ,Iran

Background: Co- word analysis is one of the content analysis methods used in scientometric studies and mapping the scientific structure of various fields. The purpose of the present research is to map the structure of distance education using the co-word analysis. Methods: The research method is content analysis using co- word analysis. The research population are 31607 documents indexed in the field of distance education domain in the Web of Science database from 1985 to 2016. For data analysis, the UCInet and BibExcel softwares have been used. In this research, the symmetric matrix as well as the cluster analysis and the strategic diagram was used for analyzing the data. Results: The findings showed that the concepts of electronic learning and blended learning had the highest frequency in distance education research. The pairs of e-learning- blended learning , e-learning-education and training , and higher education-e-learning with 446, 328, and 302 word co-occurrences respectively, and took the first to third places in the field of distance education studies. Findings on hierarchical clustering led to the formation of 13 clusters in this field. Conclusion: The results of this study showed that based on the co- word analysis, the structure of the distance education is composed of thirteen clusters as follows: The process of designing e-learning environments , E-literacy , The role of information and communication technologies in the process of teaching and learning , Strengthening the process of virtual teaching and learning , Educational scenario , educational planning and Individual learning style and Learning and teaching quality , Human interaction in the virtual environment , educational feedback , Educational system , and Miscellaneous . Newly emerged fields of distance education include human interaction in the virtual environment , educational feedback , and learning system .

Co-occurrence of words, Distance education, Co-word analysis, Knowledge structure