When you reference an encyclopedia as a source in your paper, your citation will reflect that you are referencing a work with articles and -- in the case of a print encyclopedia -- volumes. Different styles of citation provide different formats for referencing your encyclopedia sources.
American Psychological Association
To cite an encyclopedia article in APA, include the name of the article as well as the volume number and page where it is located in addition to the author name, title and publication information, as follows:
Barnes, J. (1998). Horses. In The Encyclopedia Britannica. (Vol. 14, pp. 217-223). Chicago, IL: The Encyclopedia Britannica.
To cite an online encyclopedia, include the URL in place of the publication info. If no author is listed, use the name of the encyclopedia in place of the author name:
The Encyclopedia Britannica. (2013). Transylvania. Retrieved from http://www.britannica.com/EBchecked/topic/603323/Transylvania
Modern Language Association
In MLA format, the article title is placed in quotes. The type of publication -- print or Web -- is included at the end of your citation:
Barnes, James. "Horses." The Encyclopedia Britannica. Vol. 14. Chicago: The Encyclopedia Britannica, 1998. Print.
MLA Web citations do not require a listed URL. Instead, note the last date you accessed the website at the end of your citation. In place of the publication information, include the name of the website in italics followed by the name of the organization that operates the website. Include both items, even if the organization name is the same as the website name:
"Transylvania". The Encyclopedia Britannica. The Encyclopedia Britannica, 2013. Web. 9 April 2015.
In APA format, the author name and year are included as a parenthetical in-text citation following a quote or reference. The page number is included for direct quotes but is optional for paraphrasing: (Barnes, 1998. p. 220) If no author is available, include the article title in quotes in the author's place: ("Transylvania").
When doing in-text citations in MLA, include only the author name and page number: (Barnes 220). For an encyclopedia article without an author, use the name of the article instead: ("Transylvania").