Radiographic dating definition

(The classification of definitions as nominal or real is conventional.)Up to now we have been discussing explicit definitions, which not only permit the Dfd to be introduced into any context as an “abbreviation” for the Dfn but also, in contrast, permit the Dfd to be taken out of an arbitrary context, when necessary, and be “decoded” by means of the Dfn.A classic example of this type of definition may be the definitions examined by Aristotle, per genus et differentiam (”by kind and specific difference”), which affirm the equality of the Dfd and Dfn, in which the Dfd is singled out from some wider class of objects (genus) by indicating one of its specific properties (differentia).The rule of univocacy (or definiteness) is the natural requirement of uniqueness of the Dfd for each Dfn—but, of course, not the reverse. (Although it guarantees the absence of homonymy within a particular theory, the rule of univocacy does not preclude synonymy. Sometimes implicit definitions may be transformed into explicit, or contextual definitions.(The process of solving a system of equations is an example of such a transformation, inasmuch as it may be regarded, from the outset, as the definition, albeit implicit, of the unknowns.) Cases in which the implicit nature of the definition cannot be removed are of particular importance.Insofar as pointing out an object (or class of objects)—a method characteristic of ostensive definition—may be accomplished with words alone (using demonstrative pronouns and descriptions, for example), it is natural to include such linguistic structures in the same class of definitions.However, the overwhelming majority of definitions, in which both the Dfd and the Dfn are verbal, define the meanings of certain expressions (the Dfd) through the meanings of other expressions (the Dfn) that are assumed to be known (within the bounds of the given definition).

In physics and other natural sciences, these requirements are fulfilled by using operational definitions—that is, definitions of physical quantities by a description of the operations by means of which they are measured, and definitions of properties of objects by a description of the reactions of these objects to specific experimental actions.They fulfill the requirement of efficiency in the construction of the Dfd and in the discrimination of the Dfd from objects not satisfying the given definition.These requirements are very much in accord with the mathematically important criterion of constructibility, the measurability of the quantity introduced by the given definition.Definitions of all kinds (including those considered above) must fulfill a number of general requirements (principles), the violation of which may invalidate a proposition that formally resembles a definition. The rule of interchangeability (eliminability), which constitutes a requirement of equivalence between the Dfd and the Dfn of real definitions, stipulates the possibility of interchanging the Dfd and Dfn of explicit nominal definitions.