Profit Margin
The percentage of revenue remaining after costs are subtracted. Gross margin excludes operating expenses; net margin includes all costs. Margin measures efficiency at converting revenue to profit.
Biological Context
Profit margin is the business equivalent of net energy gain in biology. Like Darwin's finches selecting seeds where beak-to-seed match yields positive energy returns, companies should pursue markets where their capabilities yield positive margins. A large-beaked finch chasing tiny seeds expends more energy than it gains—negative margin. The 1977 Galápagos drought killed finches whose beak-seed mismatch meant negative energy margins. In biology, the currency isn't revenue (calories consumed)—it's margin (net energy after foraging costs).
Business Application
Companies obsessed with revenue growth while ignoring margin are like animals eating food that costs more energy to catch than it provides. Unit economics matter. A customer that costs $150 to acquire and generates $100 lifetime value has negative margin—each new customer makes the company weaker, not stronger. The finch doesn't care about 'gross seeds consumed'—only net energy gained.