Define the term "specific fuel consumption" regarding gas turbines.

Specific fuel consumption (SFC) is a key parameter in evaluating the efficiency of gas turbines. It quantifies the fuel efficiency of the engine, which is the amount of fuel consumed relative to the power produced. Specifically, SFC is expressed as the amount of fuel burned per hour (in units such as pounds or kilograms) for each unit of horsepower generated. This measurement allows for comparison between different gas turbine engines and helps assess their operational efficiency.

In the context of the options provided, this makes the understanding of SFC critical for operational analysis and engineering evaluations. Other choices relate to parameters that do not directly describe fuel efficiency, such as airflow in the compressor, power output, or the physical characteristics of the turbine itself.