Mich. Comp. Laws § 691.1401

Sec. 1. As used in this act: (a) "Governmental agency" means this state or a political subdivision. (b) "Governmental function" means an activity that is expressly or impliedly mandated or authorized by constitution, statute, local charter or ordinance, or other law. Governmental function includes an activity performed on public or private property by a sworn law enforcement officer within the scope of the law enforcement officer's authority, as directed or assigned by his or her public employer for the purpose of public safety. (c) "Highway" means a public highway, road, or street that is open for public travel. Highway includes a bridge, sidewalk, trailway, crosswalk, or culvert on the highway. Highway does not include an alley, tree, or utility pole. (d) "Municipal corporation" means a city, village, or township or a combination of 2 or more of these when acting jointly. (e) "Political subdivision" means a municipal corporation, county, county road commission, school district, community college district, port district, metropolitan district, or transportation authority or a combination of 2 or more of these when acting jointly; a district or authority authorized by law or formed by 1 or more political subdivisions; or an agency, department, court, board, or council of a political subdivision. (f) "Sidewalk", except as used in subdivision (c), means a paved public sidewalk intended for pedestrian use situated outside of and adjacent to the improved portion of a highway designed for vehicular travel. (g) "State" means this state and its agencies, departments, commissions, courts, boards, councils, and statutorily created task forces. State includes a public university or college of this state, whether established as a constitutional corporation or otherwise. (h) "Township" means a general law township or a charter township. (i) "Volunteer" means an individual who is specifically designated as a volunteer and who is acting solely on behalf of a governmental agency.