ORDER By N., Pam M.S. - April 7, 2013 noun. With regard to biological taxonomy, a primary subset of a category, consisting of a set of like, corresponding families. ORDER: "The order is expressed with numbers, and the classes by letters, in the textbook." Related Psychology Terms PHYLUM VARIETY KINGDOM CONCEPT SPECIES GENUS PARAPSYCHOLOGY THYROXINE (T4) DOMAIN BIOLOGICAL FACTOR Cite this page: N., Pam M.S., "ORDER," in PsychologyDictionary.org, April 7, 2013, https://psychologydictionary.org/order/ (accessed January 19, 2021).