What you're actually paid for
The economic definition
In standard labour economics, work is compensated human activity that produces valuable transformation. A surgeon turns a diseased body into a healthier one. A teacher turns an uninformed student into an informed one. A carpenter turns timber into a house. The compensation is what makes it economic activity; the transformation is what makes it valuable.
The energy-and-information view
Thermodynamic economists — notably Robert Ayres and Benjamin Warr — point out that every act of production is energy flowing through something to rearrange matter or process information. In this view, human labour is one particular way of supplying that energy and that information. It is not the only way, and historically has been displaced piece by piece.
What people actually pay for
Customers do not pay for hours of human activity as such. They pay for outcomes: a working roof, a healthy heart, a clean floor, a correct tax return. Hours are often how we measure and invoice, but they are not what is being bought. This distinction matters when a non-human can deliver the same outcome.
Why the two definitions matter
If you think of labour primarily as human effort, automation looks inevitable as machines get cheaper. If you think of it as something that contains irreducibly human elements — care, judgment, accountability, meaning — the picture becomes more nuanced. Most honest analysis uses both lenses.
Pick a job you know well. Can you describe what it does in purely physical terms — what matter or information gets rearranged?