(1) The word "authorities" shall mean the board of trustees or the commission vested by law with the duty of operating the public schools in any particular district, unit or county of the State;

(2) The term "operating school unit" shall mean any type of school district, whether it be located in its entirety in one county or located partly in more than one county or, in case the schools of any county be operated by the county unit plan, the county;

(3) The term "capital improvements" shall mean the constructing, improving, equipping, renovating and repairing of school buildings or other school facilities or the cost of the acquisition of land whereon to construct or establish such school facilities; and

(4) The term "county board" shall mean the county board of education of the county wherein the operating school unit is located, except that when an operating school unit is located partly in one county and partly in another county such term shall in such instances relate to the county boards of education of the counties wherein the operating school unit is located.