Comparative advantage
Etymology
The idea is credited to David Ricardo, who laid it out in his 1817 Principles of Political Economy and Taxation, using the famous example of England and Portugal trading cloth and wine. Some historians note that James Mill or Robert Torrens may have reached the insight around the same time, so sole credit to Ricardo is a convenient simplification. The word "comparative" is doing the essential work — the advantage is measured against your own alternatives, not against the other party.
noun phrase · /kum-PAIR-uh-tiv ad-VAN-tij/
The principle that you should specialize in what you give up the least to produce, even when someone else is better than you at everything.
What it names
The counterintuitive truth that trade and delegation pay off based on relative, not absolute, skill — so a brilliant surgeon should still hire a gardener, and a small country still has something worth trading.
Example
She could format the slides faster than her assistant, but her comparative advantage is closing deals, so she hands the deck off without guilt.
Related idea
Absolute advantage asks who is better in raw terms; comparative advantage asks who sacrifices less to do it, which is why it hinges on opportunity cost rather than skill.