Here's why:
* Primary sources are original materials, like letters, diaries, photographs, or scientific data.
* Secondary sources analyze and interpret primary sources, like biographies, historical accounts, or journal articles.
* Tertiary sources summarize and synthesize information from both primary and secondary sources. Encyclopedias, textbooks, and dictionaries fall into this category. They provide an overview of a topic by condensing information from multiple sources.
So, while encyclopedias can be incredibly helpful for getting a basic understanding of a topic, it's important to remember that they are not primary sources of information.