Short Run (Production)
Plain definition
The period in which at least one input — typically capital like buildings and machinery — is fixed and cannot be changed.
In economics
In microeconomics, the short run is a conceptual period, not a fixed number of months: it lasts as long as some input is fixed. Short-run decisions concern how much of the variable inputs (labor, raw materials) to use with given capital, producing the familiar SR cost curves.
Example
A factory with a fixed-size plant can hire more workers or run extra shifts (short-run decisions), but it cannot build a second plant — that expansion is a long-run decision.
The short run is often confused with 'the near future.' In economics it means any period with a fixed input, whether that lasts weeks or years; a power utility's short run can be decades because plants are so slow to build.