In simple yet profound terms, variation represents the difference between an ideal and an actual situation.
An ideal represents a standard of perfection—the highest standard of excellence[1]—that is uniquely defined by stakeholders, including direct customers, internal customers, suppliers, society and shareholders.
Excellence is synonymous with quality, and excellent quality results from doing the right things, in the right way.
The fact that we can strive for an ideal but never achieve it means that stakeholders always experience some variation from the perfect situations they envision. This, however, also makes improvement and progress possible. Reducing the variation stakeholders experience is the key to quality and continuous improvement.
References
An ASQ LinkedIn discussion on the topic of the definition of quality
ASQ Glossary – Law of Variation — 2005 – 2018~. Identifies the interrelationship between variation, perfection, quality, and excellence. What is the Law of Variation_ Managing Variation _ ASQ
ASQ Glossary Law of Variation – Updated 2018~ NEW What is Variation
Quality Leadership 