1. A formal examination, correction, and official endorsing of financial accounts: An audit normally takes place in businesses and is undertaken annually by an accountant.
2. A systematic check or assessment: The efficiency or effectiveness of an organization or a process is accomplished by an audit that is typically carried out by an independent assessor.
3. In computer programming: a process used to detect accidental input or processing errors as well as fraud: Audits often use test data and special-purpose software.
4. In computer programming: a set of procedures which are established to ensure the quality and integrity of a data base: Audits also carry out the processes and procedures of ensuring the data base quality and integrity.
5. Etymology: from Latin auditus, "a hearing"; past participle of audire, "to hear".

It now stands for the official examination of business accounts, which were originally oral or spoken. The verb is from about 1557.

1. To attend an academic class or seminar informally without receiving academic credit for it: Carol wanted to audit a German class and learn some of the language, but she was not interested in getting any recognition of her achievement.
2. To examine and correct an official financial report; inspect: Mr. Smart was asked to audit, or to inspect, the accounts of the treasurer.
3. To scrutinize and evaluate something thoroughly: Mr. Goodman was an auditor and was appointed to audit and verify the correctness of the accounts regarding the property of the firm.