In Citations and Your Credibility, construction site expert witness William Gulya, Jr., President & CEO, Middlesex Trenching Company writes:
It is essential to recognize that each of various types of citations and reference listing styles has a specific format that must be followed. Loosely, a citation is a reference to a published or unpublished source (not necessarily the original source). More precisely, “a citation is an abbreviated alphanumeric expression (e.g., [Example 79]) embedded in the body of an intellectual work that denotes an entry in the bibliographic references section of the work for the purpose of acknowledging the relevance of the works of others to the topic of discussion at the spot where the citation appears” (Wikipedia, (Unknown). Retrieved Sept. 18, 2009, from http://en.wikipedia.org/wiki/Citation). Generally the combination of both the in-body citation and the bibliographic entry constitutes what is universally considered a citation.