Mass. Gen. Laws ch. 78 § 24
The following words and phrases used in sections twenty-two to thirty-one, inclusive, shall, unless the context otherwise requires, have the following meanings:
"Board," the board of library commissioners.
"Professional librarian," a person qualified by education, training or study and experience to practice library work in a position requiring knowledge of books and of library aims and techniques equivalent to that attained through graduation from a library school accredited by the American Library Association.
"Subprofessional librarian," a person in the opinion of the board qualified through an elementary knowledge of library techniques to engage in the necessary library routines involved in the acquiring and circulation of books but not qualified as a professional librarian.
Mass. Gen. Laws ch. 78, § 24