The definition of a primary source varies depending upon the academic discipline and the context in which it is used.
The nature of a source is determined by the way a researcher makes use of it. The same item might be considered a primary source in one investigation and a secondary source in another. For example, a speech about the Declaration of Independence that was delivered by a noted statesman on its hundredth anniversary would be secondary source for a scholar studying the document’s philosophical origins. But, it would be a primary source for a scholar studying how the Declaration’s meaning has changed for Americans over time.
The value of a source is also determined by its use. A memoir written by a signer of the Declaration of Independence years after the event would be of much more importance to a historian studying the debates of the Continental Congress than would the diary entry of an individual who lived in Philadelphia in 1776, but had no personal interaction with the Congress or its members.
The sources available to you in your undergraduate research could often be more accurately described as primary source surrogates. For example, instead of examining an individual’s diary directly, you may find yourself using reproduced images of its pages or, more likely yet, a typed transcription of its contents. Or, instead of experiencing a sculpture firsthand, you may be dependent upon photographs of it. Obviously, some primary source surrogates are better than others.
If you are unsure of what would be considered a primary source for your particular project, ask your professor for examples. The following is an incomplete list of things that might be considered primary sources by different academic disciplines.