noun
negative spread; loss margin; back spread
Financial term for a situation where the cost of funds exceeds the return on investment, or more broadly any unfavorable margin. Often used in banking and securities contexts.
金利が上昇すると、銀行の逆ざやが拡大する。
When interest rates rise, the bank's negative spread widens.
この投資は逆ざやで、利益が出ない。
This investment is in a loss margin and won't yield a profit.
Compound of 逆 (reverse) and 鞘 (margin, spread). The financial sense of 鞘 comes from the image of a scabbard as a container, metaphorically extended to the difference between two prices.