Long Run (Production)
Plain definition
The period in which all inputs, including capital, can be varied — the firm can change plant size, enter, or exit the industry.
In economics
In the long run there are no fixed costs; every input is a choice. Firms plan their scale by tracing the long-run average cost curve (LRAC), an envelope of short-run ATC curves. Long-run decisions include building new factories and choosing technology.
Example
Over the long run, a carmaker can close an old plant, build a new one, or switch to a more automated production process — all inputs, including capital, are adjustable.
The long run is not 'far away in time.' It is defined by the flexibility of inputs: for a roadside stall the long run may be months, for an airline decades. Do not confuse it with long-run equilibrium in macroeconomics, which is a different concept.