Definition:

Acceptance Criteria are the specific conditions or requirements that a product, feature, or user story must satisfy to be considered complete. They establish a shared understanding of what “done” means and ensure that the delivered work meets the stakeholder’s expectations.

Example:

For a user login feature, the Acceptance Criteria might include:

Users can log in with valid credentials.

An error message is displayed for invalid credentials.

The system locks out users after three failed attempts.