comm. law. A letter containing information of any circumstances unknown to the person to whom it is written; generally informing him of some act done by the writer of the letter. 2. It is usual and perfectly proper for the drawer of a bill of exchange to write a letter of advice to the drawee, as well to prevent fraud or alteration of the bill, as to let the drawee know what provision has been made for the payment of the bill. Chitt. Bills 185. (ed. of 1836.)