Etymology is the study of historical linguistic change, which occurs due to the development of a particular word or element of a word, often delineating its spread from one language to another and its evolving changes in form and meaning. They're explanations of what our words meant and how they sounded 600 or 2,000 years ago. The impact factor of journal provides quantitative assessment tool for grading, evaluating, sorting and comparing journals of similar kind. It reflects the average number of citations to recent articles published in science and social science journals in a particular year or period, and is frequently used as a proxy for the relative importance of a journal within its field. It is first devised by Eugene Garfield, the founder of the Institute for Scientific Information.