For the purposes of this Act, the expression “maintenance order” means an order other than an order of affiliation for the periodical payment of sums of money towards the maintenance of the wife or other dependants of the person against whom the order is made, and the expression “dependants” means such persons as that person is, according to the law in force in the part of His Majesty’s dominions in which the maintenance order was made, liable to maintain; the expression “certified copy” in relation to an order of a court means a copy of the order certified by the proper officer of the court to be a true copy, and the expression “prescribed” means prescribed by rules of court.