the.com/profit margin

means The slice of revenue left over as profit after all costs are paid, usually expressed as a percentage of sales.

from 'Profit' traces back through French to Latin profectus, meaning 'progress' or 'advance' — the sense of material gain grew out of the idea of moving forward. 'Margin' comes from Latin margo, meaning edge or border, like the blank space at the side of a page. Put together in commercial English, the phrase pictures profit as the narrow edge left over at the boundary between what you earn and what you spend — the thin strip where a business actually gets ahead.