An abstraction; a general idea inferred or derived from specific instances. (Oxford Dictionaries Online 2012)
Oxford Dictionaries Online S.v. "Concept" Accessed February 20, 2012. http://oxforddictionaries.com/definition/concept.
A concept is an abstraction; a general idea inferred or derived from specific instances. For example, by viewing a pet dog, one can infer that there are other dogs of that “type.” Hence, from this observation (or perhaps a set of observations) the concept of a dog is developed in one's mind. Concepts are bearers of meaning, as opposed to agents of meaning and can only be thought about, or designated, by means of a name.
principles depend on concepts in order to state a “truth.” Hence, principles and concepts go hand in hand; principles cannot exist without concepts and concepts are not very useful without principles to help guide the proper way to act (Lawson and Martin 2008).
Lawson, H., and J.N. Martin. 2008. "On the Use of Concepts and Principles for Improving Systems Engineering Practice". Proceedings of the 18th Annual International Council on Systems Engineering (INCOSE) International Symposium, 5-19 June 2008, Utrecht, The Netherlands.