Architecture is what's expensive to change

Architecture represents the significant design decisions that shape the form or function of a system, where ‘significant’ is measured by the cost of change.” —Grady Booch

Because our metaphors aren’t perfect, it can be hard to figure out what parts of an experience “count” as architecture. At its core, architecture is what is too expensive to change frequently. It’s the slow pace layers: the site and structure that must enable many different possibilities in the faster layers.