New York Civil Practice Law
Form of Civil Judicial Proceedings
(a) One form of action. There is only one form of civil action. The distinctions between actions at law and suits in equity, and the forms of those actions and suits, have been abolished.
(b) Action or special proceeding. All civil judicial proceedings shall be prosecuted in the form of an action, except where prosecution in the form of a special proceeding is authorized. Except where otherwise prescribed by law, procedure in special proceedings shall be the same as in actions, and the provisions of the civil practice law and rules applicable to actions shall be applicable to special proceedings.
(c) Improper form. If a court has obtained jurisdiction over the parties, a civil judicial proceeding shall not be dismissed solely because it is not brought in the proper form, but the court shall make whatever order is required for its proper prosecution. If the court finds it appropriate in the interests of justice, it may convert a motion into a special proceeding, or vice-versa, upon such terms as may be just, including the payment of fees and costs.