'亏本' literally combines '亏' (kuī), meaning 'to lose' or 'to fall short', and '本' (běn), meaning 'capital' or 'principal investment'. Together, they form a verb meaning 'to incur a financial loss' — specifically, when revenue from a business activity or investment falls below the original cost. It emphasizes that the operation failed to recoup its initial outlay, not just that profit was low.

This term is commonly used in commerce, small-business contexts, and personal finance discussions. Unlike general terms for 'loss' like '损失', '亏本' always implies a monetary shortfall relative to invested capital. It's neutral in register but carries a slightly negative connotation — indicating poor performance or misjudgment. You’ll often see it in spoken reports ('这单生意亏本了'), written summaries ('全年亏本'), or warnings ('小心定价太低会亏本').