Operational means working, functioning, and ready to use. When a new subway line becomes operational, trains start running and people can actually ride it. When a spacecraft is operational, all its systems are working properly and it's ready for its mission.

The word describes something that has moved beyond the planning or building stage into actual use. A factory under construction isn't operational yet, but once the machines are installed, tested, and producing goods, it becomes operational. A pilot might check that all the plane's controls are operational before takeoff, making sure everything responds correctly.

In business and organizations, operational often refers to the day-to-day work of actually running things. The operational side of a restaurant means cooking food, serving customers, and keeping things clean, as opposed to planning the menu or designing the building. Operational costs are the ongoing expenses of keeping something running: electricity, supplies, and wages.

Something operational actively performs its intended function. When engineers say a new invention is fully operational, they mean it works exactly as intended and is ready for real-world use.