永续合约里多空双方每隔几小时互相支付的一笔费用，用来让合约价格贴近现货价格。A fee paid between long and short traders every few hours in perpetual futures contracts, designed to keep the contract price close to the spot price.
费率为正，说明做多的人付钱给做空的人，市场整体偏向看涨且这种押注已经比较拥挤；费率为负则反过来。它是观察市场情绪是否过于一边倒的一个直接信号。A positive rate means longs are paying shorts — the market is leaning bullish and that bet is getting crowded. A negative rate means the opposite. It gives you a direct read on whether sentiment has become heavily one-sided.