One who, or that which, operates or produces an effect.
- One who operates a machine or device: a switchboard operator.
- The owner or manager of a business or an industrial enterprise.
- One who deals aggressively in stocks or commodities.
- Informal A person who is adept at accomplishing goals through shrewd or unscrupulous maneuvers.
- Mathematics A function, especially one from a set to itself, such as differentiation of a differentiable function or rotation of a vector.
- A logical operator.
- Genetics A chromosomal segment of DNA that regulates the activity of the structural genes of an operon by interacting with a specific repressor.