 Why adopt the contextual theory of meaning for scientific terms? Suppose the notion of meaning is understood along the lines of the Fregean notion of sense. The sense of a term be understood as that what determines its reference (cf. Church 1956: 6n). It is, furthermore, a reasonable requirement that a semantic theory must account for our understanding of the sense and, hence, our methods of determining the extension of scientific terms (cf. Dummett 1991: 340). For a large number of scientific terms these methods rest upon axioms of one or more scientific theories. There is no way of determining the force function in classical mechanics without using some axiom of this theory. Familiar methods make use of Newton’s second law of motion, Hooke’s law, the law of gravitation etc. Likewise, virtually all methods of measuring temperature rest upon laws of thermodynamics. Take measurement by a gas thermometer which is based on the ideal gas law. The laws of scientific theories are thus essential to our methods of determining the extension of scientific terms. The contextual theory of meaning, therefore, makes intelligible how students in a scientific discipline and scientists grasp the meaning, or sense, of scientific terms. On this account, understanding the sense of a term means knowing how to determine its referent, or extension, at least in part.