Hi
From the Scrum guide we know that:
- no changes are made that would endanger the Sprint Goal
- Quality goals do not decrease; and,
- Scope may be clarified and re-negotiated between the Product Owner and Development Team as more is learned.
From the Scrum glossary we have this definition:
Sprint Goal: a short expression of the purpose of a Sprint, often a business problem that is addressed. Functionality might be adjusted during the Sprint in order to achieve the Sprint Goal.