Since quality is used to compare things, it is ultimately associated with one's expectation on the product or service. There might many scientific, objective or industrial methods to compare quantitatively or benchmark products or services. It is user's expectation that counts most to the perception of quality in a product or service. Therefore, I would define quality as:
Quality product or service is product or service that satisfies or exceeds its user's expectation.Since expectation is such a fluid measure, any claims that rush to claim, that a product or service has met user's expectation, is almost guaranteed a failure. Needless to mention the ever growing nature of human expectation. Therefore, it is impossible for anyone to claim that user's expectation is met. Furthermore, even user's current expectation can be met technically, it may be well above the user's affordability. Due to this reason, I would refine the definition into:
Quality product or service is product or service that satisfies its agreed characteristics or criteria.In software development, the agreed characteristics and criteria should be translated into user's requirements and acceptance criteria to the software product.
