Mass. Gen. Laws ch. 142 § 1
In this chapter the following words shall have the following meanings:
"Certificate", a certificate of registration issued in accordance with section three of chapter five hundred and thirty-six of the acts of nineteen hundred and nine, section two of chapter five hundred and ninety-seven of the acts of nineteen hundred and ten or chapter five hundred and eighteen of the acts of nineteen hundred and twelve.
"Certificate of a plumbing corporation or certificate of a plumbing partnership", a certificate of registration issued to a master plumber authorizing him to conduct the plumbing business as a corporation or as a partner in a partnership, as the case may be.
"Certificate of a gas fitting corporation or certificate of a gas fitting partnership", a certificate of registration issued to a master gas fitter authorizing him to conduct the gas fitting business as a corporation or as a partner in a partnership, as the case may be.
"Examiners", the board of state examiners of plumbers and gas fitters appointed under section thirty-six of chapter thirteen.
"Gas fitting", any work which includes the installation, alteration, and replacement of a piping system beyond the gas meter outlet or regulator through which is conveyed or intended to be conveyed fuel gas of any kind for power, refrigeration, heating or illuminating purposes including the connection therewith and testing of gas fixtures, ranges, refrigerators, stoves, water heaters, house heating boilers, and any other gas using appliances, and the maintenance in good and safe condition of said systems, and the making of necessary repairs and changes.
"Journeyman gas fitter", a person who himself does any work in gas fitting, subject to inspection under any law, rule or regulation.
"Journeyman plumber", a person who himself does any work in plumbing and gas fitting, subject to inspection under any law, rule or regulation.
"Master gas fitter", a gas fitter, having a regular place of business and who, by himself or journeyman gas fitters in his employ, performs gas fitting work, subject to inspection and in compliance of any law, rule or regulation pertaining to same.
"Master plumber", a plumber having a regular place of business and who, by himself or journeyman plumbers in his employ, performs plumbing and gas fitting work, subject to inspection and in compliance with any law, rule, or regulation pertaining to same.
"Plumbing", the work and practice, materials and fixtures used in the installation, removal, maintenance, extension, and alteration of a plumbing system; of all piping, fixtures, fixed appliances, and appurtenances in connection with any of the following: sanitary drainage, storm drainage facilities, special wastes, the venting system and the public or private water-supply systems, within or adjacent to any building, structure, or conveyance; to their connection with any point of public disposal or other acceptable terminal within the property line.
"Apprentice gas fitter", a person who is learning and working at the business of gas fitting under the direct supervision of a master plumber, master gas fitter, journeyman plumber or journeyman gas fitter.
"Apprentice plumber", a person who is learning and working at the business of plumbing under the direct supervision of a master plumber or journeyman plumber.
"Registered", registered in accordance with section three of chapter five hundred and thirty-six of the acts of nineteen hundred and nine, section two of chapter five hundred and ninety-seven of the acts of nineteen hundred and ten or chapter five hundred and eighteen of the acts of nineteen hundred and twelve.
"Undiluted liquefied petroleum gas installer", a person who does any work in installing undiluted liquefied petroleum gas systems and appliances.
"Limited undiluted liquefied petroleum gas installer", a person who does any work in installing, connecting and moving from place to place undiluted liquefied petroleum gas salamanders, space heaters and related equipment used in buildings under construction.
Mass. Gen. Laws ch. 142, § 1