My favorite analogy to describe the difference between architecture and design is to use the analogue of highway / street maps. I you were driving from New York to Los Angeles, you might approach mapping out your route the way we (should) approach architecture and design. At the most abstract level (the architecture), we understand that we have states, cities and within states, and interstate highways. To start, all we really need to know is which states we want to go through, and what interstates we want to take to optimize our time. This is an architectural approach. At this level of abstraction, all interstates can be treated much the same and while we know that the road systems within each city are different, that level of detail is not important (at this point in time).
Once we understand the basic path from NY to LA and approximately where we want to stop, we zoom-in to each specific area, focusing on its specific design and how to get from the Interstate to the points of interest, hotels, etc. and back again. Many cities even follow a similar pattern, where there is a “ring road” that encircles the city and interconnects to the highway system, but not all fit this pattern. Many small towns fit the pattern of having a “Main Street” that serves as its thoroughfare. Patterns help us understand the city / town road systems, as they give us a degree of familiarity, even in an unfamiliar place.
In this analogy, architecture and design are clearly related. Architecture is more abstract, focusing on the whole to gain perspective, and on the patterns that underlie similarities in the parts. Design focuses in on one or more parts and lets the broader picture “fade into the background”, so to speak.
This analogy works pretty well to distinguish the concepts of architecture and design as long as we recognize that the delineation is really just a “Point of View”. In other words, the fact that we have treated the city / town road systems as design elements is only really based on the fact that our scope in the example was the whole United States and we drew out patterns between cities and towns in different states.
If we reset our scope to a single city, for example we could just as easily talk about the “architecture” of the city’s road system, with more detailed elements being boroughs and districts within the city.
The important point to recognize is that architecture focuses on the whole to gain perspective, by abstracting away detail in order to draw higher level relationships. Architectural patterns capture “what is the same” about groups of elements within the architecture. Design, on the other hand is about the detail. In order to get the necessary detail, you zoom in, allowing elements beyond your “design scope” to fall outside “the field of view”. To put these in perspective with other design elements, we can think of “zooming-out” to the architecture level, moving to a different part of the map and “zooming back in” again.
At the risk of confusing rather than clarifying and to mix metaphors: Architecture is about the forest. Design is about the trees.