1. Composition or combination of parts or elements so as to form a whole, particularly the combination of often varied and diverse ideas, forces or factors into one coherent or consistent complex.
2. An interdisciplinary bringing together of major groups of sciences which have a mutual correlation, or as a bringing together of two or three sciences which were already rather closely allied.
3. One of the stronger conceptions of the unity of science suggests the existence of a model or pattern of scientific theory, of which each particular theory is an instance, so that higher level sciences recapitulate, although with more complex elements, the structure of lower level sciences, with genuine novelty emerging at each new level. Although reduction is not a necessary part of this synthetic view, the sciences are nearly always arranged in a hierarchy in which a part-whole relationship of some sort is held to obtain between levels, although the wholes may not be explainable without residue in terms of the parts. The sciences thus form a totality, the unit of which is provided by the archetypal structure that reappears at each stage.