Mass. Gen. Laws ch. 215 § 1
The probate and family court department established under section one of chapter two hundred and eleven B shall consist of divisions, one for each county, and wherever the words "probate court", "court of insolvency" or "probate and insolvency court" are used, or similar words importing the same, or wherever in this chapter the word "court" is used in that context, they shall refer to a division of the probate and family court department; and the words "judge of probate", "judge of probate and insolvency" or the word "judge", in context, shall mean an associate justice of the trial court appointed to a division of the probate and family court department; and the words "register of probate", "register of probate and insolvency" or the word "register", in context, shall mean the register of a division of the probate and family court department; and the words "registry of probate", "registry of probate and insolvency" or the word "registry", in context, shall mean the registry of said division.
Probate courts shall be courts of record, and the judge and the register of probate for each county shall be, respectively, the judge and the register of the division within the probate and family court department for that county.
Mass. Gen. Laws ch. 215, § 1