User stories are a key component in Agile practices, including the Disciplined Agile (DA) framework. They are typically described by the acronym INVEST, which stands for:

Independent: User stories should be self-contained, so they do not overlap with others.

Negotiable: User stories are not contracts; they should leave room for discussion and refinement.

Valuable: Each user story must deliver value to the end user or customer.

Estimable: A good user story can be estimated in terms of the effort required to complete it.

Small: User stories should be small enough to be completed within a single iteration.

Testable: A user story must be testable, meaning it should be possible to determine whether the user story has been completed successfully.

Based on the INVEST criteria, "Achievable" is not a recognized feature of a user story. While achieving a user story is an implicit goal, it is not explicitly mentioned in the standard definition or characteristics used in Agile frameworks such as Disciplined Agile. The features that are essential to a user story are "Negotiable," "Estimable," and "Testable," as they ensure the story is clearly defined, measurable, and valuable to the user.

References:

Disciplined Agile Delivery: A Practitioner's Guide to Agile Software Delivery in the Enterprise, Scott Ambler & Mark Lines.

PMI’s Disciplined Agile Scrum Master (DASM) and Disciplined Agile Senior Scrum Master (DASSM) training materials.