Massachusetts General Laws Part I. Administration of the Government (Ch. 1-182) Ch. 43, § 99

A majority of all the members elected to the city council shall constitute a quorum. The mayor, if present, shall preside at the meetings and may vote. In the absence of the mayor, the vice-chairman of the city council shall preside and, in the absence of both, a temporary chairman shall be chosen, who shall serve during the absence of both the mayor and the vice-chairman. The city clerk shall be, ex-officio, clerk of the city council, and shall keep records of its proceedings; but, in case of his absence or disability or of a vacancy in the office, the city council shall elect a temporary clerk, who shall be sworn to the faithful discharge of his duties and shall act as clerk of the city council until the city clerk resumes his duties or a new city clerk is qualified. All final votes of the city council on questions involving the expenditure of fifty dollars or more, or upon the request of any member any vote of the city council, shall be by yeas and nays and shall be entered on the records. The affirmative vote of a majority of all the members elected to the city council shall be necessary for the passage of any order, ordinance, resolution or vote, except that the affirmative vote of a majority of the members present shall be sufficient to adjourn any meeting of the city council.