Longman Dictionary of Contemporary English
Wiktionary
n. (context historiography English) A historical document that was created at or near the time of the events studied, by a known person, for a known purpose
Wikipedia
In the study of history as an academic discipline, a primary source (also called original source or evidence) is an artifact, a document, diary, manuscript, autobiography, a recording, or other source of information that was created at the time under study. It serves as an original source of information about the topic. Similar definitions are used in library science, and other areas of scholarship, although different fields have somewhat different definitions. In journalism, a primary source can be a person with direct knowledge of a situation, or a document written by such a person.
Primary sources are distinguished from secondary sources, which cite, comment on, or build upon primary sources. Generally, accounts written after the fact with the benefit (and possible distortions) of hindsight are secondary. A secondary source may also be a primary source depending on how it is used. For example, a memoir would be considered a primary source in research concerning its author or about his or her friends characterized within it, but the same memoir would be a secondary source if it were used to examine the culture in which its author lived. "Primary" and "secondary" should be understood as relative terms, with sources categorized according to specific historical contexts and what is being studied.
Usage examples of "primary source".
Howell Petroleum, especially Howell Petroleum (Venezuela), was his primary source of crude petroleum and petroleum products.
As cryptanalysis repeatedly demonstrated its abilities and worth, it rose from an auxiliary to a primary source of information about the foe.
While (hey were waiting for the arrival of the other colonists, Richard's robots had been their primary source of amusement.
That would eliminate the primary source of this hideous contamination, the home nest of the enemy.
He wished desperately he could leave the Down Time and share his news with Ianira now, but he had several hours left on his shift and she would be in the middle of a session with an uptime graduate student, one of many who consulted-and paid-her as a singular, primary source.
Place, it is now recognized, is no longer a primary source of diversity.
Redmond and his people, in fact, were the primary source of information on local conditions and politics used by Army Intelligence in preparing for the invasion.
Therefore, although the sun formed the primary source of light for the whole system, the heat that warmed the world below came from the gas-giant's thermal radiation.
It was what made at least three of those moons capable of life support in spite of long periods when the moons hid from the primary source of their energy.
This usually happens only if the victim was the primary source of food for a vampire for an extended period of time.
Do you think she got it from some primary source in and around the hospital, or do you think she got it from Nodelman?
After an hour's perusal of stations 2 to 27 on the Benuil's TV system, the Battlemaster decided that the host creatures used the visual mode as the primary source of information, and commented on the visual material through the audio.
Jessica had finally formulated an image of this: the creature angled its leaf-vanes at the primary source of light, reflecting and concentrating beams to make the meaningful patterns.
I think the primary source of psychic phenomena is the human mind, not the human body.