1. A Is for Atomicity: The principle of atomicity states that all parts of a transaction must complete, or none of them.
2. C Is for Consistency: The principle of consistency states that the results of a query must be consistent with the state of the database at the time the query started.
3. I Is for Isolation: The principle of isolation states that an incomplete (that is, uncommitted) transaction must be invisible to the rest of the world.
4. D Is for Durability: The principle of durability states that once a transaction completes with a COMMIT, it must be impossible for the database to lose it.