What makes the GDP gap a type of opportunity cost?

The GDP gap represents the difference between a country's potential economic output and its actual output, highlighting the resources that are underutilized. This gap indicates the economic opportunities lost by not achieving full production, which can result in lower income, employment, and public services. Consequently, the GDP gap reflects an opportunity cost, as the economy forgoes potential growth and benefits that could have been realized if resources were fully employed. Thus, it illustrates the trade-offs associated with inefficiencies in economic performance.