The word "periodical" refers to magazines, newspapers, and scholarly journals. Newspapers and popular magazines like People, or Road and Track, are familiar to everyone. Scholarly journals (also called academic, professional, or peer-reviewed journals), are written by experts for other experts. They are considered more authoritative than most other sources, because each article is written by experts and reviewed by a panel of experts from the same field before publication. In-depth research will usually require you to find scholarly journal articles on your subject.
| Popular magazines | Scholarly journals |
| Use everyday language | Use technical language |
| Written for the general reader | Written for experts by other experts |
| Do not include references to sources of information used to write the article | Include a list of references at the end of the article |
| Are often colorful and designed to attract attention | Often have dull covers and titles like "Journal of ...," "Proceedings of ..." |
Most of the EBSCOhost databases have a check-off option for scholarly journals, making it easy to limit your search to peer-reviewed publications.
The ScienceDirect interface does not have such a checkoff option, but apart from the magazine New Scientist, the articles found on ScienceDirect are scholarly.
The same general characteristics apply to scholarly books: they use technical language, are written by experts for experts, and employ "scholarly apparatus" such as detailed references giving the sources of information used. There are also books which, although they are not "scholarly" in the same sense, are highly specialized, and are intended for a reader in a specific field. (An example is Safe operation of fire tankers, published by the U.S. Fire Administration.)
There is no "checkoff" option in the catalog to determine scholarly/popular status. In general, you must look at the book, examine its language, and determine its intended audience in order to determine whether it is popular or scholarly/field specific.