The Journal Impact Factor (JIF), from Journal Citation Reports, is defined as "citations to the journal in the JCR year to items published in the previous two years, divided by the total number of scholarly, citable items published in the journal in the previous 2 years." For example:
Source: Journal Citation Reports: A Primer on the JCR and Journal Impact Factor
Journal impact measurements reflect the importance of a particular journal in a field and take into account the number of articles published per year and the number of citations to articles published in that journal. Like author impact measurements, journal impact measures can be only so informative, and researchers in a discipline will have the best sense of the top journals in their field.
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