Section 1. As used in this chapter, the following words shall, unless the context clearly requires otherwise, have the following meanings:—
''Bank'', an association or corporation chartered by the commonwealth under chapter 167H, 168, 170 or 172.
''Board'', the board of trustees or directors in a bank.
''Capital stock'', the sum of the par value of the preferred and common shares of capital stock of a stock corporation, issued and outstanding.
''Commissioner'', the commissioner of banks.
''Mutual bank'', an association or corporation chartered by the commonwealth under chapter 168 or 170 which is in mutual form.
''Stock corporation'', a savings bank under chapter 168, a co-operative bank under chapter 170, which has been chartered, converted or reorganized to a stockholder form of corporation or a trust company under chapter 172.
''Surplus account'', an account so designated on the books of a bank and consisting of amounts required by law.