Primary sources are materials in a variety of formats, created at the time under study, that serve as original evidence documenting a time period, event, people, idea, or work. Primary sources can be printed materials (such as books and ephemera), manuscript/archival materials (such as diaries or ledgers), audio/visual materials (such as recordings or films), artifacts (such as clothes or personal belongings), or born-digital materials (such as emails or digital photographs). Primary sources can be found in analog, digitized, and born-digital forms.
Secondary sources are works that synthesize and/or comment on primary and/or other secondary sources. Secondary sources, which are often works of scholarship, are differentiated from primary sources by the element of critical synthesis, analysis, or commentary.
These definitions are taken from the ACRL Guide for Primary Source Literacy
Some topics to consider when evaluating primary sources:
Download this list as a handout:
Download a sample rubric for evaluating Primary Sources from Indiana University Bloomington:
In the sciences, it is easiest to understand the definition of primary source by connecting the publication cycle to the knowledge cycle.
After an idea is discussed, developed, and tested, preliminary findings are shared through conference presentations, research posters, or through technical or company reports. The full results of research is published in scholarly journals, theses, or dissertations. There can also be some exceptions, such as a technical report published by a company sharing the full results of the research, but between these two steps of the knowledge and publication cycle is where the primary research is shared.
The secondary and tertiary sources like popularizing the results through magazines or generalizing the information for an encyclopedia come later on in the cycle. Confusion for students generally stems from the fact that the sciences are different from the humanities. Journal articles are not primary sources in those disciplines, and especially for general education classes, you may have a mix of majors taking your course.