Diminishing returns
Etymology
The concept was formalized in classical economics, notably by Anne-Robert-Jacques Turgot in the eighteenth century and later Ricardo and Malthus, originally to describe farm output as you added more labor to a fixed plot of land. "Diminishing" comes from Latin diminuere, "to make smaller," and "return" here means yield on an input. In everyday use it has broadened from agriculture to any effort-versus-payoff relationship, sometimes conflated loosely with negative returns, where more input actually makes things worse.
noun phrase · /dih-MIN-ish-ing ri-TURNZ/
The pattern where each additional unit of effort or input yields progressively less benefit than the one before it.
What it names
The reason the first hour of studying, the first slice of pizza, and the first hire on a project each deliver more than the tenth — a curve that governs when to stop pushing and reallocate.
Example
We’ve hit diminishing returns on polishing the pitch deck — the next three hours will barely move it, so let’s practice delivery instead.
Related idea
Diminishing returns still means each unit adds something, just less; negative returns is the further point where additional input actively subtracts value, as when adding a fifth cook to a small kitchen slows dinner.