Perfection is a state, variously, of completeness, flawlessness, or supreme excellence. The term is used to designate a range of diverse, if often kindred, concepts. These have historically been addressed in a number of discrete disciplines, notably mathematics, physics, chemistry, ethics, aesthetics, ontology, and theology. Term and concept The form of the word long fluctuated in various languages. The English language had the alternates, "perfection" and the Biblical "perfectness." The word "perfection" derives from the Latin "perfectio", and "perfect" — from "perfectus". These expressions in turn come from "perficio" — "to finish", "to bring to an end". "Perfectio(n)" thus literally means "a finishing", and "perfect(us)" — "finished", much as in grammatical parlance ("perfect"). Many modern languages have adopted their terms for the concept of "perfection" from the Latin: the French "parfait" and "perfection"; the Italian "perfetto" and "perfezione"; the Spanish "perfecto" and "perfección"; the English "perfect" and "perfection"; the Russian "совершенный" (sovyershenniy) and "совершенcтво" (sovyershenstvo); the Croatian and Serbian "savršen" and "savršenstvo"; the Czech "dokonalost"; the Slovak "dokonaly" and "dokonalost"; the Polish "doskonały" and "doskonałość". The genealogy of the concept of "perfection" reaches back beyond Latin, to Greek. The Greek equivalent of the Latin "perfectus" was "teleos". The latter Greek expression generally had concrete referents, such as a perfect physician or flutist, a perfect comedy or a perfect social system. Hence the Greek "teleiotes" was not yet so fraught with abstract and superlative associations as would be the Latin "perfectio" or the modern "perfection". To avoid the latter associations, the Greek term has generally been translated as "completeness" rather than "perfection". The oldest definition of "perfection", fairly precise and distinguishing the shades of the concept, goes back to Aristotle. In Book Delta of the Metaphysics, he distinguishes three meanings of the term, or rather three shades of one meaning, but in any case three different concepts. That is perfect: 1. which is complete — which contains all the requisite parts; 2. which is so good that nothing of the kind could be better; 3. which has attained its purpose. The first of these concepts is fairly well subsumed within the second. Between those two and the third, however, there arises a duality in concept. This duality was expressed by Thomas Aquinas, in the Summa Theologica, when he distinguished a twofold perfection: when a thing is perfect in itself — as he put it, in its substance; and when it perfectly