Chemical reactions, fluid mechanics, heat transfer, and mass transfer have both direct and indirect interactions. The direct ones, which are examined here, involve the effects of the fundamental mechanisms of reaction and transport on one another. The indirect ones, which arise from combined reactors, heat exchangers, and separators, are to be examined separately. Although most of the direct interactions have been recognized for decades, the investigations of such phenomena experimentally, theoretically, and numerically are very limited in number and scope. Furthermore, they are scarcely mentioned in textbooks on either chemical reaction engineering or transport. They could readily be incorporated in the software for computer-aided process design but have not, possibly because of the significant added complexity but more likely because of a lack of recognition of their importance or even their existence. In a supplementary investigation, selective numerical calculations have shown that, although the interactions between reaction and transport are of second order in magnitude in some applications, they are critical in others. Accordingly, in another supplementary investigation, new concepts, generalizations, and asymptotes have been devised to encompass these interactions and thereby abet their inclusion in future textbooks and software.