Final answer:
A ledger is the book of accounts that records the financial effects of a firm's transactions, using T-accounts for assets and liabilities and serving as a unit of account.
Step-by-step explanation:
The blank in the question should be filled with 'ledger.' A ledger is a book of accounts that reflects the financial effects of the firm's transactions after they are posted from the varying journals. This crucial component of the financial recording process helps in the preparation of financial statements. Within the ledger, individual accounts are often kept in the form of T-accounts, which are a balance sheet representation with a two-column format. The T-shape is formed by the vertical line down the middle and the horizontal line under the column headings for Assets and Liabilities. The ledger, acting as a unit of account, enables the measurement of market values in an economy. It is important not just for the present but also for understanding the future financial position of a company.