Briefly saying, Quality can be defined as: degree of excellence – oxford dictionary; Fitness for purpose – Edward Deming; Best for the customer’s use and selling price – Feigenbaum; The totality of characteristics of an entity that bear on its ability to satisfy stated or implied needs – ISO.

While measure software development quality, there are some factors:

1. Reliability

2. Maintainability

3. Usability

4. Portability

5. Correctness

6. Efficiency

7. Integrity or security

8. Testability

9. Flexibility

10. Reusability

11. Interoperability

We can determine whether system meets the requirements of quality or not with these quality attributes standards.

Source: http://www.softwaretestinghelp.com/what-are-the-quality-attributes/