ACID is an acronym for atomicity, consistency, isolation, and durability.

• Atomicity (A) - transaction is applied in full, or not at all;
• Consistency (C) - in the end of transaction, integrity constraints must be met;
• Isolation (I) - parallel transactions generate same results as in single-user environment;
• Durability (D) - database states must be valid until they are changed by transaction.

This abbreviation expresses that all transactions in a database lead from a consistent state to a new consistent state of the database.¹

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1. MEIER, Andreas; KAUFMANN, Michael. (2019) SQL & NoSQL Databases. Models, Languages, Consistency Options and Architectures for Big Data Management. Wiesbaden: Springer Vieweg. ISBN 978-3-658-24548-1 ↩︎