Mass. Gen. Laws ch. 145 § 2
The following words used in this chapter shall have the following meanings:
"Acceptance of this chapter" shall include the acceptance of corresponding provisions of earlier laws.
"Basement", a story partly but not more than one half below the level of the adjacent ground.
"Cellar", a story more than one half below the level of the adjacent ground.
"Corner lot", a lot situated at the junction of two streets, each not less than twenty feet in width. Any part of the width of such lot distant more than seventy feet from such junction shall not be regarded as part of a corner lot, but shall be subject to the provisions of this chapter respecting interior lots.
"Court", an open unoccupied space, other than a yard, on the same lot with the tenement house. A court not extending to the street or yard is an "inner court". A court extending to the street or yard is an "outer court".
"Existing", existing at the time of the acceptance of this chapter or corresponding provisions of earlier laws.
"Fireproof tenement house", one constructed of fireproof material throughout, with floors built of iron, steel or re-enforced concrete beams, filled in between with terra cotta or other masonry arches or with concrete or re-enforced concrete slabs; wood may be used only for under and upper floors, windows and door frames, sashes, doors, interior finish, hand rails for stairs, necessary sleepers bedded in the cement, and for isolated furrings bedded in mortar. There shall be no air space between the top of any floor arches and the floor boarding.
"Front" of a lot, that boundary line which borders on the street. In the case of a corner lot, the owner may elect by statement on his plans either street boundary line as the front.
"Half story", any story included in the roof of which the floor area of the rooms is not more than seventy-five per cent of the area of the ground floor.
"Height" of a tenement house, the perpendicular distance measured in a straight line from the curb level, or from the finished grade line of the lot, where such grade is higher than the curb, to the highest point of the roof beams in the case of flat roofs, and to the average of the height of the gable in the case of pitched roofs, the measurements in all cases to be taken through the centre of the facade of the house. Where a building is on a corner lot and there is more than one grade or level, the measurements shall be taken through the centre of the facade on the street having the lowest elevation.
"Interior lot", any lot other than a corner lot.
"Lodging house" or "boarding house", any house or building, or part thereof, in which six or more persons are harbored, received or lodged for hire, or any building, or part thereof, which is used as a sleeping place or lodging for six or more persons not members of the family residing therein.
"Nuisance" includes all public nuisances as known at common law or in equity jurisprudence; and furthermore whatever is dangerous to human life or detrimental to health, whatever building or erection, or part or cellar thereof, is overcrowded with occupants or is not provided with adequate ingress and egress to and from the same, or the apartments thereof, or is not sufficiently supported, ventilated, sewered, drained, cleaned or lighted, in reference to their or its intended or actual use, and whatever renders the air or human food or drink unwholesome, are also severally in contemplation of this chapter, nuisances; and all such nuisances are hereby declared unlawful.
"Occupied spaces". Outside stairways, fire escapes, porches, platforms and other projections shall be considered as part of the building and not as part of the yard or courts or unoccupied area.
"Public hall", a hall, corridor or passageway not within an apartment.
"Rear" of a lot, the side opposite to the front. In the case of a triangular or gore lot the rear shall be the side not bordering on the street.
"Stair hall", the stairs, stair landings and those parts of the public halls through which it is necessary to pass in going from the entrance floor to the roof.
"Street", any right of way dedicated to public use, any public alley, railroad right of way, cemetery or public park, twenty feet or more in width.
"Tenement house", any house or building, or part thereof, which is rented, leased, let or hired out to be occupied, or is occupied or is intended, arranged or designed to be occupied as the home or residence of more than two families (a family may consist of one or more persons) living independently of each other and having a common right in the halls, stairways, yard, cellar, sinks, water closets or privies, or any of them, and includes lodging and boarding houses, apartment houses, and flat houses. Dwelling houses built in continuous rows of more than two houses occupied or intended, arranged or designed to be occupied as the home or residence of one family or more having a common right in or using in common the halls, stairways, yards, cellars, sinks, water closets or privies, or any of them, shall be deemed to be tenement houses and shall be subject to all the provisions of this chapter.
"Thereafter", after the acceptance of this chapter or corresponding provisions of earlier laws.
"Wooden building", a building of which the exterior walls or a part thereof are wood.
"Yard", an open unoccupied space in the same lot with a tenement house between the extreme rear line of the house and the extreme rear line of the lot. An open unoccupied space between the front line of the house and the front line of the lot is a "front yard". A "side yard" shall be deemed an outer court on the lot line.
Words used in the present tense include the future; words in the masculine gender include the feminine and neuter; the word "shall" is always mandatory, and denotes that the house shall be maintained in all respects according to the mandate as long as it continues to be a tenement house; wherever the words "by-laws", "regulations", "building inspector" or "board of health" occur in this chapter they shall be construed as if followed by the words "of the town in which the tenement house is situated"; wherever the words "is occupied" are used in this chapter applying to any building they shall be construed as if followed by the words "or is intended, arranged or designed to be occupied".
Mass. Gen. Laws ch. 145, § 2