Quality means to differentiate the class criteriaclase from the attributes criteria..

Class gives the level regarding price (high class, high price, class of product of greater standing: Bohemian porcelain coffee cup versus plastic coffee cup).

Quality means reaching an adequate standard for use. It is not possible to be satisfied with any criteria (objective quality indicators), which is below what is expected as compliance with user expectations.

For this reason, it could also be defined as innate quality, an absolute and universally acknowledged characteristic, and which is highlighted by techniques such as QFD (Quality Function Deployment).

Referring to the process, quality is to do things well from the beginning, i.e., that the product is well produced (maximum value of use), and at the lowest possible cost. It is the result of an energetic and committed attitude, of clear efforts from a design or a talented execution, from the idea to the delivery of the product.

Definitions of acknowledged and expert organisations in the quality world are:
• Definition of ISO 9000: "Quality: Degree in which a collection of inherent characteristics complies with requirements".

• Royal Academy of the Spanish Language: "Property or collection or properties inherent to a thing that enable it to be appreciated as better or worse that the rest of its class".

• Crosby: "Quality is compliance with requirements".

• Juran: "Quality is adaptation to the clients use".

• Feigenbaum: "Satisfaction of the client's expectations".

• Taguchi: "Quality is the lowest loss possible for society".

• Deming: "Quality is client satisfaction".

• Shewhart: "Quality as a result of the interaction of two dimensions: Subjective dimension (what the client wants) and objective dimension (What is offered)".