"Primary" and "secondary" should be understood as relative terms, with sources categorized according to specific historical contexts and what is being studied.
For example, these ideas may be used to trace the history of scientific theories, literary elements, and other information that is passed from one author to another.
In a broader sense primary sources also include artifacts like photographs, newsreels, coins, paintings or buildings created at the time.
Although many primary sources remain in private hands, others are located in archives, libraries, museums, historical societies, and special collections.
History as an academic discipline is based on primary sources, as evaluated by the community of scholars, who report their findings in books, articles, and papers.
"[13] Ideally, a historian will use all available primary sources that were created by the people involved at the time being studied.
Historians studying the modern period with the intention of publishing an academic article prefer to go back to available primary sources and to seek new (in other words, forgotten or lost) ones.
"[13] Obsolete meanings of familiar words and social context are among the traps that await the newcomer to historical studies.
Original material may be... prejudiced, or at least not exactly what it claims to be.The errors may be corrected in secondary sources, which are often subjected to peer review, can be well documented, and are often written by historians working in institutions where methodological accuracy is important to the future of the author's career and reputation.
A primary source such as a journal entry (or the online version, a blog), at best, may only reflect one individual's opinion on events, which may or may not be truthful, accurate, or complete.
Participants and eyewitnesses may misunderstand events or distort their reports, deliberately or not, to enhance their own image or importance.
[18] As an example, a government report may be an accurate and unbiased description of events, but it may be censored or altered for propaganda or cover-up purposes.
Barristers are taught that evidence in a court case may be truthful but may still be distorted to support or oppose the position of one of the parties.
[5] Moreover, the distinction between primary and secondary sources is subjective and contextual,[19] so that precise definitions are difficult to make.
Examples in which a source can be both primary and secondary include an obituary[23] or a survey of several volumes of a journal counting the frequency of articles on a certain topic.
[23] Whether a source is regarded as primary or secondary in a given context may change, depending upon the present state of knowledge within the field.
These forgeries have usually been constructed with a fraudulent purpose, such as promulgating legal rights, supporting false pedigrees, or promoting particular interpretations of historic events.
One particularly unusual forgery of a primary source was perpetrated by Sir Edward Dering, who placed false monumental brasses in a parish church.
], forged documents have been placed within the UK National Archives in the hope of establishing a false provenance.