This is not a big subject, but it is worth discussing.

Generally speaking, the categories are pretty much as given below:

1. Research – Research is the type of work that involves figuring out how something works, what laws or rules it follows.  It may or may not be pointed at a specific final application. And it may be that several separate areas of research ultimately underpin the development and design of a product.  The research may or may not be original.  Indeed it may simply be a matter of finding the research of others and cataloging it for future use.
2. Development – Development is an early stage of design in that you take what you learned from your own research and/or someone else’s research and you develop a method(s) to put the knowledge to a practical use.  Development bridges the gap between research and the design of the final product.  It is the application of the knowledge gained in research to a practical objective.  It can be simply one approach to the design or a series of approaches to the design.  And part of what is being developed is the specification(s) of what is desired in the final design in terms of performance, life, maintainability, and price.  In this case, performance is really all encompassing.  It is not just how well the design accomplishes its mission, but how easy it is to use, what resources it expends, and possibly some aesthetic issues.

1. Design – In a final sense, the design is what defines the final desired product.  The word design will show up during the development phase, but I use it here to designate the final design.  The final design will probably go through rigid test and evaluation to assure that it meets its by now firm requirements.  Failures may require backing up into the development phase to some degree in order to solve the problem(s).  Once those issues are resolved, the final design will continue to be tested at some level to be sure of the manufacturing and materials that go into the final product.  Those “acceptance tests or inspections” may vary over the life of production, but their objective is only to assure the quality of the final product.  They are not meant to be a test of the design definition.