Concept
A concept is the organising idea behind a design, the single clear intention that gives the plan, form and materials a reason to be as they are.
A concept is not a style or a mood board. It is a proposition about how the building should work: that the home should turn inward around a courtyard, that it should step down the slope rather than cut into it, or that the old cottage should be retained and the new work sit quietly behind it.
Its value is decision-making. Hundreds of choices follow across a project, and a clear concept resolves most of them, because each option can be tested against whether it strengthens or weakens the original idea.
Concepts are established early, during conceptual or schematic design, and the strongest ones remain legible in the finished building.