As used in this chapter, unless the context otherwise requires:

1. (a) “Proposal” means any proposal for the formation of a new, or change in the boundaries of an existing, district.
2. (b) “Supervising authority” means the board of supervisors, city council or the governing body authorized by law to act upon proceedings for the formation of a new, or change in boundaries of an existing, district.
3. (c) “District” means any tax, assessment or any other district except as otherwise provided in Section 58902.
4. (d) “Clerk” means the clerk or secretary of the supervising authority.
5. (e) “Principal act” means the law providing for the creation or change in boundaries of a district.