Complex sentence: A database transaction is a unit of interaction with a database management system or similar system that is treated in a coherent and reliable way independent of other transactions that must be either entirely completed or aborted.
Split into simpler sentences: A database transaction is a unit of interaction with a database management system or similar system that is treated in a coherent and reliable way independent of other transactions. In general, a database transaction must be atomic, meaning that it must be either entirely completed or aborted.