CAP stands for:

• consistency;
• availability;
• partition tolerance.

The CAP theorem states that in any massive distributed data management system, only two of the three properties - consistency, availability, partition tolerance - can be ensured.¹

Consistency in CAP is defined quite differently from what ACID defines as consistency:

• ACID consistency describes transaction consistency: transaction brings the database from one valid state to another, maintaining all the database invariants (such as uniqueness constraints and referential integrity).
• In CAP, it means the operations are atomic (operations succeed or fail in their entirety) and consistent (operations never leave the data in an inconsistent state).²

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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 ↩︎

2. Petrov, Alex (2019) Database Internals. A Deep Dive into How Distributed Data Systems Work. O'Reilly Media, Canada. ISBN 978-1-4920-4034-7 ↩︎