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# Base currency

AKA transaction currency

Currency unit prices are quoted as currency pairs. The base currency - also called the transaction currency - is the first currency appearing in a currency pair quotation, followed by the second part of the quotation, called the [quote currency](/knowledge-base/vocabulary/quote-currency.md) or the counter currency.

In a currency pair *BTC/ETH*, *BTC* is the base currency and *ETH* is the [quote currency](/knowledge-base/vocabulary/quote-currency.md).