Mass. Gen. Laws ch. 144 § 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.
"Alcove", any part of a room partitioned off by fixed or movable partitions of any material, by curtains or portieres, or by other contrivance or device, and intended or designed to be used for living purposes.
"Basement", a story partly underground but having not less than one half its height above the level of the curb, and also having one half its height in every part above the level of the adjoining ground.
"Cellar", a story more than one half below the level of the curb or adjoining ground.
"Corner lot", a lot situated at the junction or intersection of two streets each not less than sixteen feet in width, but any lot the outer angle of which is over one hundred and twenty-five degrees shall not be considered a corner lot. Any portion of the width of the front of such lot distant more than fifty feet and any portion of the depth of such lot distant more than one hundred feet from such a junction or intersection 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 or front yard, on the same lot with a tenement house. A court extending to the street, yard, front yard or side yard is an "outer court". A court not so extending is an "inner court".
"Existing", existing at the time of the acceptance of this chapter or corresponding provisions of earlier laws.
"First class construction". A tenement house of first class construction is one constructed of fireproof material throughout, with floors built of 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 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.
"First story", the lowest story, the ceiling of which is six feet or more above both the level of the curb and the level of the adjacent ground. In determining the height of any building by stories, the stories thereof beginning with such first story shall be numbered upward.
"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" or "attic", any story included in the roof, the cubic contents of which, exclusive of cockloft or blind attic not exceeding three feet in height at the highest point, is not more than sixty per cent of the cubic contents of the first story.
"Height", 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 mean height above the eaves of any sloping roof, and to the highest point of the roof beams in the case of flat roofs, except that in the case of flat roofs a parapet exceeding three feet in height shall be considered a part of the height of the building, the measurements in all cases to be taken through the centre of the street front of the house. Where a building is on a corner lot and there is more than one grade or curb level, the measurements shall be taken from the centre of the front on the street having the lowest elevation.
"Interior lot", any lot other than a corner lot.
"Lot", the plot of ground covered by and adjacent to a tenement house or dwelling house and devoted exclusively to the purposes of such house, as shown by the plan of such lot furnished to the building department pursuant to section eighty-five.
"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 or egress to and from the same or apartments thereof, or is not sufficiently supported, ventilated, sewered, drained, cleaned or lighted in reference to its or their 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 such nuisances are hereby declared unlawful.
"Occupied spaces". Porches, platforms, except those on the first story when the basement is not occupied or designed or intended to be occupied for habitation, and outside stairways, except fire escapes and steps leading to the first story, shall be considered as part of the building and not as part of the yard or courts or unoccupied areas.
"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 corner lot with streets on three sides, or of a triangular or irregularly shaped lot abutting on two streets at their junction or intersection, the rear shall be a side not bordering on a street.
"Second class construction". A tenement house of second class construction is one of which the exterior and party walls are fireproof and conform to the requirements of first class construction as defined by law or by ordinance of the city in which it is situated.
"Stair hall" includes 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" includes any right of way dedicated to public use, any public alley, or railroad right of way sixteen feet or more in width, any cemetery or public park.
"Tenement house", any house or building, or part thereof, which is rented, leased, let or hired out, to be occupied, or is occupied, or intended, arranged or designed to be occupied as the home or residence of two or more families (a family may consist of one or more persons), living independently of each other and doing their cooking on the premises and having a common right in the halls, stairways, yard, courts, cellar, sinks, water closets or privies, or any of them. Where the occupants of dwelling houses contiguous and vertically divided, each occupied or intended, arranged or designed to be occupied as the home or residence of one family or more, have a common right in or use in common the halls, stairways, yards, cellars, sinks, water closets or privies, or any of them, such dwelling houses shall be deemed to be tenement houses and shall be subject to this chapter.
"Thereafter", after the acceptance of this chapter or corresponding provisions of earlier laws.
"Third class construction". A tenement house of third class construction is one of which the exterior walls or parts thereof are of combustible materials and do not conform to the requirements of first class construction.
"Yard", an open unoccupied space on the same lot with the tenement house between the extreme rear line of the house and the extreme rear line of the lot. A "front yard" is an open unoccupied space between the front line of the house and the front line of the lot. A "side yard" is an open unoccupied space between the side line of the main part of the house and the side line of the lot and 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 feminine and neuter; the word "shall" is always mandatory, and denotes that the house shall be maintained in all respects according to the mandate so long as it continues to be a tenement house; whenever the words "charter", "ordinances", "regulations", "building department", "building inspector", "health department", "board of health", "department charged with the enforcement of this chapter", or "city solicitor" occur in this chapter they shall be construed as if followed by the words "of the city in which the tenement house is situated"; wherever the words "is occupied" are used in this chapter applying to any building, such words shall be construed as if followed by the words "or is intended, arranged or designed to be occupied".
Mass. Gen. Laws ch. 144, § 2