Double entry. The system of bookkeeping by which two entries, one credit and one debit, are
made of every transaction.  In double entry a day-book, journal and ledger are the essential
books, although a cash-book, bill-book, stock-book, invoice-book, etc., are usually added. By the
double entry system every transaction is made to appear on the record as both debtor and
creditor by observance of the principle that, in every instance, the thing obtained is debtor to the
thing given and the thing given is creditor of the thing obtained.