A subsidy was an allocation of money by a government to an organization or service to help pay for its costs. This was generally done for such things which benefited the public and did not make sufficient money on their own.
In 2372, First Minister Shakaar Edon's adjutant Sarish Rez suggested that Shakaar mention his recent increase of transit subsidies to the crowd gathered on Deep Space 9's Promenade to see him. He also asked Shakaar to mention that, as a result of the subsidies, the cost to travel between Bajor and Deep Space 9 should begin to drop within a few months. (DS9: "Crossfire")