Section 1. The following words as used in this chapter shall, unless the context otherwise requires, have the following meanings:

''Officer'', ''officers'' and ''administrative officers'', when used without further qualification or description, any person or persons in charge of any department or division of the city. The said words when used in contrast with a board or members of a board, or with division heads, shall mean any of the persons in sole charge of a department of the city.

''Ordinance'', a vote or order of the city council entitled ''ordinance'' and designed for the permanent regulation of any matter within the jurisdiction of the city council as laid down in this chapter.

''Plan A'', a city government and legislative body composed of the mayor and a city council, the councillors being elected at large.

''Plan B'', a city government and legislative body composed of a mayor and city council, the councillors being elected partly at large and partly from districts or wards of the city.

''Plan C'', a city government and legislative body composed of a mayor and commissioners as hereinafter specified.

''Plan D'', a city government and legislative body, to be known as the city council, composed of seven or nine members, one of whom shall be mayor and shall be the official head of the city, and an administrative officer, called the city manager.

''Plan E'', a city government and legislative body, to be known as the city council, composed of seven or nine members, one of whom shall be elected as mayor by and from such members and shall be the official head of the city, and an administrative officer, called the city manager; the members of the city council and the elective members of the school committee to be elected at large by proportional representation.

''Plan F'', a city government and legislative body composed of a mayor and a city council, the councillors being elected partly at large and partly from wards of the city, with the mayor and city councillors to be nominated in party primaries.

''An optional plan of a city council and a school committee organization in certain large cities'', a legislative body, to be known as the city council, composed of at least nine members or a school committee composed of at least nine members, or both, elected from equally populous districts and one member of the city council or of the school committee elected at large for every one hundred and twenty thousand residents of the city in excess of one hundred and fifty thousand residents, notwithstanding its plan of government or charter.

''Elected at large'', elected by and from all the voters of the city.

''Proportional representation'', any proportional representation method of election authorized by sections ninety-three to one hundred and sixteen, inclusive.

''Regular municipal election'', the annual or biennial election of municipal officers for which provision is made in this chapter.