be·hav·ior (b?-h?v?y?r)n.1. The manner in which one acts or behaves.2. a. The actions or reactions of a person or animal in response to external or internal stimuli.b. One of these actions or reactions: “a hormone … known to directly control sex-specific reproductive and parenting behaviors in a wide variety of vertebrates” (Thomas Maugh II).3. The manner in which something functions or operates: the faulty behavior of a computer program; the behavior of dying stars.[Middle English behavour, from behaven, to behave (on the model of havour, behavior, from Old French avoir, from avoir, to have); see behave.]be·hav?ior·al adj.be·hav?ior·al·ly adv.Synonyms: behavior, conduct, bearing, deportment, comportment, demeanor These nouns all pertain to a person’s actions as they constitute a means of evaluation by others. Behavior is the most general: The children were on their best behavior. Conduct applies to actions considered from the standpoint of morality and ethics: “Life, not the parson, teaches conduct” (Oliver Wendell Holmes, Jr.). Bearing often carries with it the implication of social standing or position: “It was evident from his bearing that he belonged to the country’s ruling élite” (Amitav Ghosh). Deportment and comportment pertain more narrowly to actions measured by a prevailing code of social behavior: “the alleged decline in standards of deportment?a significant issue for an institution that prided itself on turning out ‘gentlemen'” (Jerome Karabel).”Would I see a different person, or merely the same one governed by different conventions of comportment … accoutrement, and dress?” (Witold Rybczynski). Demeanor suggests outward appearance that manifests inward emotion or character: “The Beth I saw now was not only nimble-footed, but her demeanor was exuberant and self-assured” (Rachel Simon).American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.be?hav?ior (b??he?v y?r) n. 1. the manner of conducting oneself. 2. Psychol., Animal Behav. a. observable activity in a human or animal. b. the aggregate of responses to internal and external stimuli. c. a stereotyped species-specific activity, as a courtship dance. 3. the action or reaction of any material under given circumstances. [1400?50; late Middle English behavoure, behaver, derivative of behave, on the model of hav(i)or possession