To make by putting parts together in order. Also the particular made thing that results from one such making.
Old English byldan (to build), from bold (a house, a dwelling), from Proto-Germanic *buth-la-, related to 'bower' and, distantly, to 'be'; to build was first specifically to make a dwelling.
The order the parts go together in is load-bearing rather than incidental, so undoing a build usually means starting over rather than adjusting one piece — and the noun sense freezes that ordered process at a moment worth naming and returning to.