Mass. Gen. Laws ch. 217 § 1
For each county there shall be a division of the probate and family court department of the trial court, and in each division, except those for Suffolk, Middlesex, Essex, Worcester, Plymouth, Hampden, Bristol, Norfolk and Barnstable counties, one appointment of an associate justice of the trial court shall be made, and he shall be the justice for that division. 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 of the trial court; 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 said 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.
Mass. Gen. Laws ch. 217, § 1