Sources of historical information or evidence are often categorized as primary, secondary, or tertiary material. These classifications are based on the originality of the material and the proximity of the source or origin. This informs the reader as to whether the author is reporting information that is first hand or is conveying the experiences and opinions of others which is considered second hand. Determining if a source is primary, secondary or tertiary can be tricky. Below you will find a description of the three categories of information and examples to help you make a determination.
Primary sources are the "raw materials" and foundation of historical research and writing. They are the primary (basis) from which historians collect and start their historiography. These sources are records of events or evidence as they are first described or actually happened without any interpretation or commentary. It is information that is shown for the first time or original materials on which other research is based. Primary sources display original thinking, report on new discoveries, or share contemporary or fresh information.
These sources offer an analysis or restatement of primary sources. They often try to describe or explain primary sources. They tend to be works which summarize, interpret, reorganize, or otherwise provide an added value to a primary source.
Tertiary sources are based exclusively on secondary sources – i.e., on the research of others. These are sources that index, abstract, organize, compile, or digest other sources. Some reference materials and textbooks are considered tertiary sources when their chief purpose is to list, summarize or simply repackage ideas or other information. Tertiary sources are usually not credited to a particular author.