Transaction cost refers to any cost incurred in the process of buying or selling a good or service. There are a few synonyms for transaction cost, including cost of exchange, market friction, and trading expense. The cost of exchange refers to any expenses that come with doing business with a particular counterparty. Market friction describes any impediments that can affect efficiency in the market, while trading expense refers to all costs incurred specifically in the process of executing a trade. Regardless of the term used, transaction costs can often play a significant role in the overall profitability of business transactions. It's important for businesses to carefully consider these costs when making decisions.