Trading Pair

Every trading pair follows a base/quote structure: the price tells you how many units of the quote asset are needed to buy one unit of the base asset. In an order book, a BTC/USDT price of 65,000 means one bitcoin costs 65,000 USDT, and buy or sell orders are matched at whatever price both sides agree on. Which asset sits on which side of the slash is a convention set by the exchange, not an arbitrary label.

The choice of quote currency has shifted over crypto's history. Early exchanges quoted most altcoins in BTC itself, since Bitcoin had the deepest liquidity and fiat on-ramps were scarce. Today the dominant quote assets are large stablecoins like USDT and USDC, which give traders a dollar-equivalent unit without touching a bank; some regulated exchanges also offer direct fiat pairs such as BTC/USD or ETH/EUR. BTC/USDT and ETH/USDT remain the most traded pairs by volume across major venues, though stablecoin-to-stablecoin pairs like USDC/USDT sometimes see comparable turnover from arbitrage and treasury flows rather than directional trading.

On a decentralized exchange, there is usually no order book at all. A trading pair instead exists as a liquidity pool holding both assets in a fixed ratio, with an algorithm setting the price as traders swap one side for the other and liquidity providers earning a share of trading fees.

Not every pair trades directly. A less common altcoin may only be listed against BTC or a stablecoin, forcing traders into two hops to reach the pair they actually want, and thinly traded pairs carry wider spreads and greater slippage risk.