Definitions of quality:

• noun:   an essential and distinguishing attribute of something or someone

  Example: "The quality of mercy is not strained--Shakespeare"

• noun:   a degree or grade of excellence or worth

  Example: "The quality of students has risen"

• noun:   a characteristic property that defines the apparent individual nature of something

  Example: "Each town has a quality all its own"

• noun:   high social status

  Example: "A man of quality"

• noun:   (music) the distinctive property of a complex sound (a voice or noise or musical sound)
• adjective:   of high social status

  Example: "People of quality"

• adjective:   of superior grade

  Example: "Quality paper"