The definition of work varies depending on the context, but here are a few common understandings:

• In physics, work is the energy transferred to or from an object by a force causing displacement. In simple terms, work is done when a force moves an object over a distance. It is calculated as the product of the force and the distance the object moves in the direction of the force. Source
• In economics, work is human effort, whether physical or mental, applied to the production of goods or services. It is a factor of production. Source
• In a general sense, work is an activity involving mental or physical effort done to achieve a purpose or result. This could include a job, a task, or any activity that requires exertion. Source

In essence, work involves expending effort to accomplish something, whether it's moving an object, creating a product, or completing a task.