$BTC

In the context of cryptocurrency trading, "BTC pair" refers to any trading pair where Bitcoin (BTC) is one of the assets. It essentially means you're trading Bitcoin for another asset, which could be another cryptocurrency or even a fiat currency. 

Here's a more detailed explanation:

Trading Pairs:

A trading pair is a combination of two assets that are traded against each other on a cryptocurrency exchange. 

BTC as an Asset:

In many trading pairs, Bitcoin is used as the base currency (the asset being purchased) or the quote currency (the asset being used to purchase). 

Examples:

BTC/ETH: This pair means you can trade Bitcoin for Ethereum (and vice versa). 

BTC/USD: This pair allows you to trade Bitcoin for U.S. dollars. 

BTC/USDT: This pair allows you to trade Bitcoin for Tether (a stablecoin pegged to the U.S. dollar).