As used in this chapter, the following words shall have the following meanings:
(1) PUBLIC AGENCY. The State of Alabama, and any county, city, town, school district, or other political subdivision of the state, any public trust, any public entity specifically created by the statutes of the State of Alabama or as a result of statutory authorization therefor, and any department, agency, board, bureau, commission, committee, or authority of any of the foregoing public entities.
(2) PUBLIC IMPROVEMENT. Any beneficial or valuable change or addition, betterment, enhancement, or amelioration of or upon any real property, or interest therein, belonging to a public agency intended to enhance its value, beauty, or utility or to adapt it to new or further purposes. The term does not include the direct purchase of materials, equipment, or supplies by a public agency, or any personal property.